Substrate holding device and polishing device

ABSTRACT

The present invention relates to a substrate holding apparatus for holding a substrate (W) such as a semiconductor wafer in a polishing apparatus for polishing the substrate to a flat finish. A substrate holding apparatus according to the present invention comprises a top ring body ( 2 ) having a receiving space therein, and a vertically movable member ( 206 ) which is vertically movable within the receiving space in the top ring body. An abutment member ( 209 ) having an elastic membrane is attached to a lower surface of the vertically movable member. The elastic membrane ( 291 ) of the abutment member comprises an abutment portion ( 291   b ), having a flange ( 291   a ) projecting outwardly, brought into direct or indirect contact with the substrate, and a connecting portion ( 291   c ) extending upwardly from a base portion ( 291   d ) of the flange of the abutment portion and being connected to the vertically movable member. The connecting portion is made of a material having a flexibility higher than the abutment portion.

TECHNICAL FIELD

The present invention relates to a substrate holding apparatus forholding a substrate to be polished and pressing the substrate against apolishing surface, and more particularly to a substrate holdingapparatus for holding a substrate such as a semiconductor wafer in apolishing apparatus for polishing the substrate to a flat finish. Thepresent invention also relates to a polishing apparatus having such asubstrate holding apparatus.

BACKGROUND ART

In recent years, semiconductor devices have become more integrated, andstructures of semiconductor elements have become more complicated.Further, the number of layers in multilayer interconnections used for alogical system has been increased. Accordingly, irregularities on asurface of a semiconductor device become increased, so that step heightson the surface of the semiconductor device tend to be larger. This isbecause, in a manufacturing process of a semiconductor device, a thinfilm is formed on a semiconductor device, then micromachining processes,such as patterning or forming holes, are performed on the semiconductordevice, and these processes are repeated many times to form subsequentthin films on the semiconductor device.

When the number of irregularities is increased on a surface of asemiconductor device, the following problems arise. The thickness of afilm formed in a portion having a step is relatively small when a thinfilm is formed on a semiconductor device. An open circuit is caused bydisconnection of interconnections, or a short circuit is caused byinsufficient insulation between interconnection layers. As a result,good products cannot be obtained, and the yield tends to be reduced.Further, even if a semiconductor device initially works normally,reliability of the semiconductor device is lowered after a long-termuse. At the time of exposure in a lithography process, if theirradiation surface has irregularities, then a lens unit in an exposuresystem is locally unfocused. Therefore, if the irregularities of thesurface of the semiconductor device are increased, then it becomesproblematic that it is difficult to form a fine pattern itself on thesemiconductor device.

Accordingly, in a manufacturing process of a semiconductor device, itincreasingly becomes important to planarize a surface of thesemiconductor device. The most important one of the planarizingtechnologies is CMP (Chemical Mechanical Polishing). In the chemicalmechanical polishing, with use of a polishing apparatus, while apolishing liquid containing abrasive particles such as silica (SiO2)therein is supplied onto a polishing surface such as a polishing pad, asubstrate such as a semiconductor wafer is brought into sliding contactwith the polishing surface, so that the substrate is polished.

This type of polishing apparatus comprises a polishing table having apolishing surface constituted by a polishing pad, and a substrateholding apparatus, which is called as a top ring or a carrier head, forholding a semiconductor wafer. When a semiconductor wafer is polishedwith such a polishing apparatus, the semiconductor wafer is held andpressed against the polishing table under a predetermined pressure bythe substrate holding apparatus. At this time, the polishing table andthe substrate holding apparatus are moved relatively to each other tobring the semiconductor wafer into sliding contact with the polishingsurface, so that the surface of the semiconductor wafer is polished to aflat mirror finish.

In such a polishing apparatus, if a relative pressing force between thesemiconductor wafer being polished and the polishing surface of thepolishing pad is not uniform over an entire surface of the semiconductorwafer, then the semiconductor wafer may insufficiently be polished ormay excessively be polished at some portions depending on the pressingforce applied to those portions of the semiconductor wafer. Therefore,it has been attempted to form a surface, for holding a semiconductorwafer, of a substrate holding apparatus by an elastic membrane made ofan elastic material such as rubber and to supply fluid pressure such asair pressure to a backside surface of the elastic membrane to unformizepressing forces applied to the semiconductor wafer over an entiresurface of the semiconductor wafer.

Further, the polishing pad is so elastic that pressing forces applied toa peripheral portion of the semiconductor wafer being polished becomenon-uniform, and hence only the peripheral portion of the semiconductorwafer may excessively be polished, which is referred to as “edgerounding”. In order to prevent such edge rounding, there has been used asubstrate holding apparatus in which a semiconductor wafer is held atits peripheral portion by a guide ring or a retainer ring, and theannular portion of the polishing surface that corresponds to theperipheral portion of the semiconductor wafer is pressed by the guidering or retainer ring.

The thickness of a thin film formed on a surface of a semiconductorwafer varies from position to position in a radial direction of thesemiconductor wafer depending on a film deposition method orcharacteristics of a film deposition apparatus. Specifically, the thinfilm has a film thickness distribution in the radial direction of thesemiconductor wafer. Since a conventional substrate holding apparatus,as described above, for uniformly pressing an entire surface of asemiconductor wafer polishes the semiconductor wafer uniformly over theentire surface thereof, it cannot realize a polishing amountdistribution that is equal to the aforementioned film thicknessdistribution on the surface of the semiconductor wafer. Therefore, theconventional polishing apparatus cannot sufficiently cope with the filmthickness distribution in the radial direction, and insufficient orexcessive polishing is caused.

Further, the aforementioned film thickness distribution on the surfaceof the semiconductor wafer varies depending on the type of a filmdeposition method or a film deposition apparatus. Specifically,positions and the number of portions having a large film thickness in aradial direction and differences in thickness between thin film portionsand thick film portions vary depending on the type of a film depositionmethod or a film deposition apparatus. Therefore, a substrate holdingapparatus capable of easily coping with various film thicknessdistributions at low cost has been required rather than a substrateholding apparatus capable of coping with only a specific film thicknessdistribution.

In a substrate holding apparatus having a structure for pressing aportion of a polishing surface that corresponds to a peripheral portionof a semiconductor wafer by a guide ring or retainer ring in order toprevent edge rounding, non-uniform polishing such as edge roundingcannot sufficiently be suppressed in some cases by merely controllingpressing forces of the aforementioned guide ring or retainer ring.Generally, no devices are formed on a peripheral portion of asemiconductor wafer. Nevertheless, for the purpose of preventing elutionof metal or other defects, it is required that a polishing rate isintentionally reduced at a peripheral portion of a semiconductor waferso that an under layer film is not exposed, or, on the contrary, apolishing rate is intentionally increased at a peripheral potion of asemiconductor wafer so as to remove a film on the peripheral potion ofthe semiconductor wafer. A conventional polishing apparatus cannotsufficiently control a polishing rate at a peripheral potion of asemiconductor wafer to a desired level.

DISCLOSURE OF INVENTION

The present invention has been made in view of the above prior art. Itis, therefore, a first object of the present invention to provide asubstrate holding apparatus and a polishing apparatus which can polish athin film, formed on a surface of a workpiece such as a semiconductorwafer, having a film thickness distribution and can obtain a uniformfilm thickness after polishing.

Further, the present invention has been made in view of the above priorart in which a polishing rate at a peripheral portion of a workpiececannot sufficiently be controlled to a desired level. It is, therefore,a second object of the present invention to provide a substrate holdingapparatus and a polishing apparatus which can uniformly polish aworkpiece such as a semiconductor wafer with controlling a polishingrate at a peripheral portion of the workpiece to a desired level.

In order to attain the first object, according to a first aspect of thepresent invention, there is provided a substrate holding apparatus forholding and pressing a substrate to be polished against a polishingsurface, characterized in that: the substrate holding apparatuscomprises a top ring body having a receiving space therein, and avertically movable member which is vertically movable within thereceiving space in the top ring body; an abutment member having anelastic membrane is attached to a lower surface of the verticallymovable member; the elastic membrane of the abutment member comprises anabutment portion, having a flange projecting outwardly, brought intodirect or indirect contact with the substrate, and a connecting portionextending upwardly from a base portion of the flange of the abutmentportion and being connected to the vertically movable member; and theconnecting portion is made of a material having a flexibility higherthan the abutment portion.

With this arrangement, pressures to be applied to the substrate canindependently be controlled, and hence a pressing force applied to athicker area of a thin film can be made higher than a pressing forceapplied to a thinner area of the thin film, thereby selectivelyincreasing the polishing rate of the thicker area of the thin film.Thus, an entire surface of a substrate can be polished exactly to adesired level irrespective of the film thickness distribution obtainedat the time the thin film is formed. Further, even if the verticallymovable member is pressed downwardly for polishing, excessive downwardforces are not applied to the substrate which is brought into closecontact with the abutment portion because the connecting portion iselastically deformed, so that a uniform polishing rate can be achievedin an area between the base portions of the flanges. Further, even if avertically movable member is lifted for polishing, excessive upwardforces are not applied to the abutment portion because the connectingportion is likely to extend, so that a vacuum is not formed near thebase portions of the flanges to achieve a uniform polishing rate in anarea between the base portions.

According to a second aspect of the present invention, there is provideda substrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: thesubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within the receiving space in the top ring body; an abutmentmember having an elastic membrane is attached to a lower surface of thevertically movable member; the elastic membrane of the abutment membercomprises an abutment portion, having a flange projecting outwardly,brought into direct or indirect contact with the substrate, and aconnecting portion extending upwardly from a base portion of the flangeof the abutment portion and being connected to the vertically movablemember; and the connecting portion comprises a thin portion having athickness smaller than the abutment portion.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of the film thicknessdistribution obtained at the time the thin film is formed.Simultaneously, even if the vertically movable member is presseddownwardly for polishing, excessive downward forces are not applied tothe substrate which is brought into close contact with the abutmentportion because the connecting portion is likely to be deformed at thethin portion, so that a uniform polishing rate can be achieved in anarea between the base portions of the flanges. Further, even if thevertically movable member is lifted for polishing, excessive upwardforces are not applied to the abutment portion because the thin portionis likely to extend, so that a vacuum is not formed near the baseportions of the flanges to achieve a uniform polishing rate in an areabetween the base portions. Particularly, when the thin portion is formedso as to be constricted inwardly in a cross-section, these effects caneffectively be achieved.

According to a third aspect of the present invention, there is provideda substrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: thesubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within the receiving space in the top ring body; an abutmentmember having an elastic membrane is attached to a lower surface of thevertically movable member; the elastic membrane of the abutment membercomprises an abutment portion, having a flange projecting outwardly,brought into direct or indirect contact with the substrate, and aconnecting portion extending upwardly from a base portion of the flangeof the abutment portion and being connected to the vertically movablemember; and adhesiveness of a lower surface of the base portion of theflange of the abutment portion is weakened.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of the film thicknessdistribution obtained at the time the thin film is formed.Simultaneously, even if the vertically movable member is lifted forpolishing, a vacuum is unlikely to be formed near the base portion ofthe flange because the base portion of the flange is unlikely to bebrought into close contact with the substrate. Therefore, a uniformpolishing rate can be achieved in an area between the base portions.

In this case, an intermediate member having a low adhesiveness to thesubstrate may be disposed on the lower surface of the base portion ofthe flange of the abutment portion to weaken adhesiveness of the lowersurface of the base portion of the flange. Alternatively, adhesivenessbetween the base portion of the flange and the substrate maybe weakenedby, for example, forming a groove in the lower surface of the baseportion of the flange, or by forming the lower surface of the baseportion as a rough surface.

According to a fourth aspect of the present invention, there is provideda substrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: thesubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within the receiving space in the top ring body; an abutmentmember having an elastic membrane is attached to a lower surface of thevertically movable member; the elastic membrane of the abutment membercomprises an abutment portion, having a flange projecting outwardly,brought into direct or indirect contact with the substrate, and aconnecting portion extending upwardly from a base portion of the flangeof the abutment portion and being connected to the vertically movablemember; and a hard member made of a material harder than the elasticmembrane is embedded in the base portions of the flange of the abutmentportion. In this case, the hard member should preferably have an annularshape.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of the film thicknessdistribution obtained at the time the thin film is formed.Simultaneously, even if the vertically movable member is downwardlypressed for polishing, excessive downward forces are not applied to thesubstrate which is brought into close contact with the abutment portionbecause downward forces by the connecting portion are dispersed by thehard member, so that a uniform polishing rate can be achieved in an areabetween the base portions. Further, even if the vertically movablemember is lifted for polishing, a vacuum is not formed near the baseportion of the flange because the hard member prevents deformation ofthe vicinity of the base portion of the flange. Therefore, a uniformpolishing rate can be achieved in an area between the base portions.

According to a fifth aspect of the present invention, there is provideda substrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: thesubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within the receiving space in the top ring body; an abutmentmember having an elastic membrane is attached to a lower surface of thevertically movable member; and the elastic membrane of the abutmentmember comprises an abutment portion, having a flange projectingoutwardly, brought into direct or indirect contact with the substrate,an extending portion extending outwardly from a base portion of theflange to a position inward of a tip of the flange to form a groovebetween the extending portion and the flange of the abutment portion,and a connecting portion extending upwardly from an outward end of theextending portion and being connected to the vertically movable member.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of the film thicknessdistribution obtained at the time the thin film is formed. Further, in acase where the vertically movable member is lifted for polishing afterthe substrate is brought into close contact with the abutment portion,upward forces by the connecting portion are converted into forces inhorizontal or oblique directions by the extending portion, and theconverted forces are applied to the base portion of the flange.Therefore, upward forces applied to the base portion of the flange canbe made extremely small, so that excessive upward forces are not appliedto the abutment portion. Accordingly, a vacuum is not formed near thebase portion, so that a uniform polishing rate can be achieved in anarea between the base portions.

According to a preferred aspect of the present invention, the connectingportion positioned radially inwardly and the connecting portionpositioned radially outwardly have different thicknesses. In this case,it is desirable that the connecting portion positioned radially inwardlyhas a thickness smaller than the connecting portion positioned radiallyoutwardly.

According to a preferred aspect of the present invention, the flangeprojecting radially outwardly and the flange projecting radiallyinwardly have different lengths. In this case, it is desirable that theflange projecting radially outwardly has a length larger than the flangeprojecting radially inwardly.

Because a cylinder having a smaller curvature generally has a stiffnesslarger than a cylinder having a larger curvature, a vertical forceapplied to the base portion of the flange by the connecting portionpositioned radially inwardly becomes larger than a force applied to thebase portion of the flange by the connecting portion positioned radiallyoutwardly. Therefore, with the above arrangement, forces applied to thebase portions of the flange positioned radially inwardly and the flangepositioned radially outwardly can be adjusted to the same level, or asealing capability can be enhanced at the flange projecting radiallyoutwardly, so that a uniform polishing rate can be achieved in an areabetween the base portions.

According to a sixth aspect of the present invention, there is provideda substrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: thesubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within the receiving space in the top ring body; an abutmentmember having an elastic membrane which is brought into direct orindirect contact with the substrate is attached to a lower surface ofthe vertically movable member; and the vertically movable member is madeof a material having a large stiffness.

With this arrangement, when the vertically movable member is made of amaterial having a large stiffness and a light weight, e.g., epoxy resin,the vertically movable member becomes unlikely to be bent, so thatpolishing rates are prevented from being locally increased. Further,when a material having no magnetism is selected as a material of thevertically movable member, the film thickness of a thin film formed on asurface of a semiconductor wafer can be measured with a film thicknessmethod using eddy current in such a state that the semiconductor waferto be polished is held.

According to a seventh aspect of the present invention, there isprovided a substrate holding apparatus for holding and pressing asubstrate to be polished against a polishing surface, characterized inthat: an abutment member having an elastic membrane is attached to alower surface of a top ring; the elastic membrane of the abutment membercomprises an abutment portion, having a flange projecting outwardly,brought into direct or indirect contact with the substrate, and aconnecting portion extending upwardly from a base portion of the flangeof the abutment portion and being connected to the top ring; and the topring has a support portion for supporting the flange of the abutmentmember.

With this arrangement, an entire surface of a substrate can be polishedexactly to a desired level irrespective of the film thicknessdistribution obtained at the time the thin film is formed.Simultaneously, when a pressurized fluid is supplied into a space aroundthe abutment member, the flange is prevented from being deformed andattached to a lower surface of the top ring, thereby achieving stablepolishing.

In this case, it is desirable that the support portion has a radiallength larger than a radial length of the flange of the abutment member.With such a support portion, the flange of the abutment member can besupported more reliably, so that more stable polishing can be achieved.

According to a preferred aspect of the present invention, a fluidintroduction groove for introducing a fluid into an upper surface of theflange of the abutment member is formed in the support portion. Withthis arrangement, since a pressurized fluid can be introduced into theupper surface of the flange, adhesiveness of the flange to the substratecan be enhanced to achieve stable polishing.

According to an eighth aspect of the present invention, there isprovided a substrate holding apparatus for holding and pressing asubstrate to be polished against a polishing surface, characterized inthat: the substrate holding apparatus comprises a top ring body having areceiving space therein, a vertically movable member which is verticallymovable within the receiving space in the top ring body, and a seal ringbeing brought into contact with an upper surface of a peripheral portionof the substrate; and the vertically movable member has a supportportion for supporting the seal ring, the support portion having aradial length in a range of from 1 mm to 7 mm.

With this arrangement, entire surface of a substrate can be polishedexactly to a desired level irrespective of the film thicknessdistribution obtained at the time the thin film is formed.Simultaneously, when a pressurized fluid is supplied into a space aroundthe seal ring, the seal ring is prevented from being deformed andattached to a lower surface of the vertically movable member. Further, aperipheral portion of the substrate is likely to be excessivelypolished. However, when the support portion has a radial length in arange of from 1 mm to 7 mm, it is possible to prevent the excessivepolishing.

According to a preferred aspect of the present invention, a fluidintroduction groove for introducing a fluid into an upper surface of theseal ring is formed in the support portion of the vertically movablemember. With this arrangement, since a pressurized fluid can beintroduced into the upper surface of the seal ring, adhesiveness of theseal ring to the substrate can be enhanced to achieve stable polishing.

In order to attain the second object, according to a ninth aspect of thepresent invention, there is provided a substrate holding apparatus forholding and pressing a substrate to be polished against a polishingsurface, characterized in that: the substrate holding apparatuscomprises a top ring body for holding the substrate, an edge bag beingbrought into contact with a peripheral portion of the substrate, atorque transmitting member being brought into contact with the substrateradially inwardly of the edge bag; and a pressure of a first pressurechamber defined in the edge bag and a pressure of a second pressurechamber defined radially inwardly of the edge bag are independentlycontrolled.

With this arrangement, sufficient torque can be transmitted to thesubstrate by the torque transmitting member. Further, the entire surfaceof the substrate except the peripheral portion thereof can be pressedagainst the polishing surface at a uniform force by the pressure of thesecond pressure chamber, and the pressure of the first pressure chambercan be controlled independently of the pressure of the second pressurechamber. Therefore, it is possible to control a polishing rate at theperipheral portion of the substrate, i.e., a polishing profile of theperipheral portion of the substrate.

According to a preferred aspect of the present invention, the torquetransmitting member has a communication hole communicating a spaceinside of the torque transmitting member and a space outside of thetorque transmitting member with each other.

Further, in view of controlling a polishing rate of a peripheral portionof the semiconductor wafer, it is desirable that the edge bag definingthe first pressure chamber comprises a member having a radial width in arange of from 1 mm to 10 mm.

According to a preferred aspect of the present invention, the substrateholding apparatus comprises a retainer ring secured to or formedintegrally with the top ring body for holding a side edge portion of thesubstrate; and a pressing force to press the retainer ring against thepolishing surface is controlled independently of a pressure of thepressure chamber. In this manner, when the pressing force of theretainer ring is also controlled, more detailed control can be achieved.

A polishing apparatus according to the present invention comprises theaforementioned substrate holding apparatus and a polishing table havinga polishing surface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing an entire arrangement of apolishing apparatus having a substrate holding apparatus according tothe present invention;

FIG. 2 is a vertical cross-sectional view showing a substrate holdingapparatus according to a first embodiment of the present invention;

FIG. 3 is a bottom view of the substrate holding apparatus shown in FIG.2;

FIG. 4 is a vertical cross-sectional view showing a first example of aring tube in the substrate holding apparatus according to the firstembodiment of the present invention;

FIG. 5 is a vertical cross-sectional view showing an elastic membrane ofa ring tube shown in FIG. 4;

FIGS. 6A through 6C are vertical cross-sectional views showingdeformation of the elastic membrane of the ring tube;

FIG. 7 is a vertical cross-sectional view showing a second example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention;

FIG. 8 is a vertical cross-sectional view showing a third example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention;

FIG. 9 is a vertical cross-sectional view showing a fourth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention;

FIG. 10 is a vertical cross-sectional view showing a fifth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention;

FIG. 11 is a vertical cross-sectional view showing a sixth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention;

FIGS. 12A through 12C are vertical cross-sectional views showing aseventh example of an elastic membrane of a ring tube in a substrateholding apparatus according to the present invention;

FIG. 13 is a vertical cross-sectional view showing a substrate holdingapparatus according to a second embodiment of the present invention;

FIG. 14 is a bottom view of the substrate holding apparatus shown inFIG. 13;

FIG. 15 is a vertical cross-sectional view showing a ring tube in thesubstrate holding apparatus according to the second embodiment of thepresent invention;

FIG. 16 is a vertical cross-sectional view showing a ring tube withoutany support portions in a chucking plate;

FIG. 17 is a partial perspective view showing a support portion of achucking plate of FIG. 15;

FIG. 18 is a vertical cross-sectional view showing a seal ring withoutany support portions in a chucking plate;

FIG. 19 is a vertical cross-sectional view showing a seal ring in thesubstrate holding apparatus of FIG. 15;

FIG. 20 is a vertical cross-sectional view showing a substrate holdingapparatus according to a third embodiment of the present invention;

FIG. 21 is a partial cross-sectional view showing an edge bag of FIG.20; and

FIG. 22 is a partial cross-sectional view showing a torque transmittingmember of FIG. 20.

BEST MODE FOR CARRYING OUT THE INVENTION

A substrate holding apparatus and a polishing apparatus according toembodiments of the present invention will be described in detail belowwith reference to the drawings.

FIG. 1 is a cross-sectional view showing an entire arrangement of apolishing apparatus having a substrate holding apparatus according tothe present invention. The substrate holding apparatus serves to hold asubstrate such as a semiconductor wafer to be polished and to press thesubstrate against a polishing surface on a polishing table. As shown inFIG. 1, a polishing table 100 having a polishing pad 101 attached on anupper surface thereof is provided underneath a top ring 1 constituting asubstrate holding apparatus according to the present invention. Apolishing liquid supply nozzle 102 is provided above the polishing table100, and a polishing liquid Q is supplied onto the polishing pad 101 onthe polishing table 100 from the polishing liquid supply nozzle 102.

Various kinds of polishing pads are available on the market. Forexample, some of these are SUBA800, IC-1000, and IC-1000/SUBA400(two-layer cloth) manufactured by Rodel Inc., and Surfin xxx-5 andSurfin 000 manufactured by Fujimi Inc. SUBA800, Surfin xxx-5, and Surfin000 are non-woven fabrics bonded by urethane resin, and IC-1000 is madeof rigid foam polyurethane (single-layer). Foam polyurethane is porousand has a large number of fine recesses or holes formed in its surface.

The top ring 1 is connected to a top ring drive shaft 11 by a universaljoint 10, and the top ring drive shaft 11 is coupled to a top ring aircylinder 111 fixed to a top ring head 110. The top ring air cylinder 111operates to move the top ring drive shaft 11 vertically to thereby liftand lower the top ring 1 as a whole and to press a retainer ring 3 fixedto a lower end of a top ring body 2 against the polishing table 100. Thetop ring air cylinder 111 is connected to a compressed air source 120via a regulator R1, which can regulate pressure of compressed air or thelike which is supplied to the top ring air cylinder 111. Thus, it ispossible to adjust a pressing force to press the polishing pad 101 withthe retainer ring 3.

The top ring drive shaft 11 is connected to a rotary sleeve 112 by a key(not shown). The rotary sleeve 112 has a timing pulley 113 fixedlydisposed at a peripheral portion thereof. A top ring motor 114 is fixedto the top ring head 110, and the timing pulley 113 is coupled to atiming pulley 116 mounted on the top ring motor 114 via a timing belt115. Therefore, when the top ring motor 114 is energized for rotation,the rotary sleeve 112 and the top ring drive shaft 11 are rotated inunison with each other via the timing pulley 116, the timing belt 115,and the timing pulley 113 to thereby rotate the top ring 1. The top ringhead 110 is supported on a top ring head shaft 117 fixedly supported ona frame (not shown).

Next, a substrate holding apparatus according to a first embodiment ofthe present invention will be described below. FIG. 2 is a verticalcross-sectional view showing the top ring 1 of the substrate holdingapparatus according to the first embodiment, and FIG. 3 is a bottom viewof the top ring 1 shown in FIG. 2. As shown in FIG. 2, the top ring 1constituting a substrate holding apparatus comprises a top ring body 2in the form of a cylindrical housing with a receiving space definedtherein, and a retainer ring 3 fixed to the lower end of the top ringbody 2. The top ring body 2 is made of a material having high strengthand rigidity, such as metal or ceramics. The retainer ring 3 is made ofhighly rigid synthetic resin, ceramics, or the like.

The top ring body 2 comprises a cylindrical housing 2 a, an annularpressurizing sheet support 2 b fitted into the cylindrical portion ofthe housing 2 a, and an annular seal 2 c fitted over an outercircumferential edge of an upper surface of the housing 2 a. Theretainer ring 3 is fixed to the lower end of the housing 2 a of the topring body 2. The retainer ring 3 has a lower portion projecting radiallyinwardly. The retainer ring 3 may be formed integrally with the top ringbody 2.

The top ring drive shaft 11 is disposed above the central portion of thehousing 2 a of the top ring body 2, and the top ring body 2 is coupledto the top ring drive shaft 11 by the universal joint 10. The universaljoint 10 has a spherical bearing mechanism by which the top ring body 2and the top ring drive shaft 11 are tiltable with respect to each other,and a rotation transmitting mechanism for transmitting the rotation ofthe top ring drive shaft 11 to the top ring body 2. The sphericalbearing mechanism and the rotation transmitting mechanism transmit apressing force and a rotating force from the top ring drive shaft 11 tothe top ring body 2 while allowing the top ring body 2 and the top ringdrive shaft 11 to be tilted with respect to each other.

The spherical bearing mechanism comprises a hemispherical concave recess11 a defined centrally in the lower surface of the top ring drive shaft11, a hemispherical concave recess 2 d defined centrally in the uppersurface of the housing 2 a, and a bearing ball 212 made of a highly hardmaterial such as ceramics and interposed between the concave recesses 11a and 2 d. On the other hand, the rotation transmitting mechanismcomprises drive pins (not shown) fixed to the top ring drive shaft 11,and driven pins (not shown) fixed to the housing 2 a. Even if the topring body 2 is tilted with respect to the top ring drive shaft 11, thedrive pins and the driven pins remain in engagement with each otherwhile contact points are displaced because the drive pin and the drivenpin are vertically movable relatively to each other. Thus, the rotationtransmitting mechanism reliably transmits rotational torque of the topring drive shaft 11 to the top ring body 2.

The top ring body 2 and the retainer ring 3 secured to the top ring body2 have a space defined therein, which accommodates therein a seal ring204 having a lower surface brought into contact with a peripheralportion of the semiconductor wafer W held by the top ring 1, an annularholder ring 205, and a disk-shaped chucking plate 206 (verticallymovable member) which is vertically movable within the receiving spacein the top ring body 2. The seal ring 204 has a radially outer edgeclamped between the holder ring 205 and the chucking plate 206 securedto the lower end of the holder ring 205 and extends radially inwardly soas to cover the lower surface of the chucking plate 206 near its outercircumferential edge. The lower end surface of the seal ring 204 isbrought into contact with the upper surface of the semiconductor wafer Wto be polished. The semiconductor wafer W has a recess defined in anouter edge thereof, which is referred to as a notch or orientation flat,for recognizing (identifying) the orientation of the semiconductorwafer. The seal ring 204 should preferably extend radially inwardly ofthe chucking plate 206 from the innermost position of such as a notch ororientation flat.

The chucking plate 206 maybe made of metal. However, when the thicknessof a thin film formed on a surface of a semiconductor wafer is measuredby a method using eddy current in a state such that the semiconductorwafer to be polished is held by the top ring, the chucking plate 206should preferably be made of a non-magnetic material, e.g., aninsulating material such as fluororesin, epoxy resin, or ceramics.

A pressurizing sheet 207 comprising an elastic membrane extends betweenthe holder ring 205 and the top ring body 2. The pressurizing sheet 207has a radially outer edge clamped between the housing 2 a and thepressurizing sheet support 2 b of the top ring body 2, and a radiallyinner edge clamped between an upper end portion 205 a and a stopper 205b of the holder ring 205. The top ring body 2, the chucking plate 206,the holder ring 205, and the pressurizing sheet 207 jointly define apressure chamber 221 in the top ring body 2. As shown in FIG. 2, a fluidpassage 31 comprising tubes and connectors communicates with thepressure chamber 221, which is connected to the compressed air source120 via a regulator R2 provided on the fluid passage 31. Thepressurizing sheet 207 is made of a highly strong and durable rubbermaterial such as ethylene propylene rubber (EPDM), polyurethane rubber,or silicone rubber.

In the case where the pressurizing sheet 207 is made of an elasticmaterial such as rubber, if the pressurizing sheet 207 is fixedlyclamped between the retainer ring 3 and the top ring body 2, then adesired horizontal surface cannot be maintained on the lower surface ofthe retainer ring 3 because of elastic deformation of the pressurizingsheet 207 as an elastic material. In order to prevent such a drawback,the pressurizing sheet 207 is clamped between the housing 2 a of the topring body 2 and the pressurizing sheet support 2 b provided as aseparate member in the present embodiment. The retainer ring 3 mayvertically be movable with respect to the top ring body 2, or theretainer ring 3 may have a structure capable of pressing the polishingsurface independently of the top ring body 2. In such cases, thepressurizing sheet 207 is not necessarily fixed in the aforementionedmanner.

A cleaning liquid passage 251 in the form of an annular groove isdefined in the upper surface of the housing 2 a near its outercircumferential edge over which the seal 2 c of the top ring body 2 isfitted. The cleaning liquid passage 251 communicates with a fluidpassage 32 via a through-hole 252 formed in the seal 2 c, and issupplied with a cleaning liquid (pure water) via the fluid passage 32. Aplurality of communication holes 253 are defined in the housing 2 a andthe pressurizing sheet support 2 b in communication with the cleaningliquid passage 251. The communication holes 253 communicate with a smallgap G defined between the outer circumferential surface of the seal ring204 and the inner circumferential surface of the retainer ring 3.

A central bag 208 and a ring tube 209 which serve as abutment membersbrought into contact with the semiconductor wafer W are mounted in aspace defined between the chucking plate 206 and the semiconductor waferW. In the present embodiment, as shown in FIGS. 2 and 3, the central bag208 is disposed centrally on the lower surface of the chucking plate206, and the ring tube 209 is disposed radially outwardly of the centralbag 208 in surrounding relation thereto. Each of the seal ring 204, thecentral bag 208, and the ring tube 209 is made of a highly strong anddurable rubber material such as ethylene propylene rubber (EPDM),polyurethane rubber, or silicone rubber.

The space defined between the chucking plate 206 and the semiconductorwafer W is divided into a plurality of spaces by the central bag 208 andthe ring tube 209. Accordingly, a pressure chamber 222 is definedbetween the central bag 208 and the ring tube 209, and a pressurechamber 223 is defined radially outwardly of the ring tube 209.

The central bag 208 comprises an elastic membrane 281 brought intocontact with the upper surface of the semiconductor wafer W, and acentral bag holder 282 for detachably holding the elastic membrane 281in position. The central bag holder 282 has threaded holes 282 a definedtherein, and the central bag 208 is detachably fastened to the center ofthe lower surface of the chucking plate 206 by screws 255 threaded intothe threaded holes 282 a. The central bag 208 has a central pressurechamber 224 defined therein by the elastic membrane 281 and the centralbag holder 282.

Similarly, the ring tube 209 comprises an elastic membrane 291 broughtinto contact with the upper surface of the semiconductor wafer W, and aring tube holder 292 for detachably holding the elastic membrane 291 inposition. The ring tube holder 292 has threaded holes 292 a definedtherein, and the ring tube 209 is detachably fastened to the lowersurface of the chucking plate 206 by screws 256 threaded into thethreaded holes 292 a. The ring tube 209 has an intermediate pressurechamber 225 defined therein by the elastic membrane 291 and the ringtube holder 292.

In the present embodiment, the pressure chamber 224 is formed by theelastic membrane 281 of the central bag 208 and the central bag holder282, and the pressure chamber 225 is formed by the elastic membrane 291of the ring tube 209 and the ring tube holder 292. The pressure chambers222, 223 may also be formed by an elastic membrane and a holder forfixing the elastic membrane, respectively. Further, elastic membranesand holders may appropriately be added to increase the number of thepressure chambers.

Fluid passages 33, 34, 35 and 36 comprising tubes and connectorscommunicate with the pressure chambers 222 and 223, the central pressurechamber 224, and the intermediate pressure chamber 225, respectively.The pressure chambers 222 to 225 are connected to the compressed airsource 120 as a supply source via respective regulators R3, R4, R5 andR6 connected respectively to the fluid passages 33 to 36. The fluidpassages 31 to 36 are connected to the respective regulators R1 to R6through a rotary joint (not shown) mounted on the upper end of the topring shaft 110.

The pressure chamber 221 above the chucking plate 206 and the pressurechambers 222 to 225 are supplied with pressurized fluids such aspressurized air or atmospheric air or evacuated, via the fluid passages31, 33, 34, 35 and 36 connected to the respective pressure chambers. Asshown in FIG. 1, the regulators R2 to R6 connected to the fluid passages31, 33, 34, 35 and 36 of the pressure chambers 221 to 225 canrespectively regulate the pressures of the pressurized fluids suppliedto the respective pressure chambers. Thus, it is possible toindependently control the pressures in the pressure chambers 221 to 225or independently introduce atmospheric air or vacuum into the pressurechambers 221 to 225. In this manner, the pressures in the pressurechambers 221 to 225 are independently varied with the regulators R2 toR6, so that the pressing forces to press the semiconductor wafer Wagainst the polishing pad 101 can be adjusted in local areas of thesemiconductor wafer W. In some applications, the pressure chambers 221to 225 may be connected to a vacuum source 121.

In this case, the pressurized fluid or the atmospheric air supplied tothe pressure chambers 222 to 225 may independently be controlled intemperature. With this configuration, it is possible to directly controlthe temperature of a workpiece such as a semiconductor wafer from thebackside of the surface to be polished. Particularly, when each of thepressure chambers is independently controlled in temperature, the rateof chemical reaction can be controlled in the chemical polishing processof CMP.

The chucking plate 206 has radially inner suction portions 261 extendeddownwardly therefrom between the central bag 208 and the ring tube 209.The chucking plate 206 has radially outer suction portions 262 extendeddownwardly therefrom outside of the ring tube 209. In the presentembodiment, eight suction portions 261, 262 are provided.

The inner suction portions 261 and the outer suction portions 262 havecommunication holes 261 a, 262 a communicating with fluid passages 37,38, respectively. The inner suction portions 261 and the outer suctionportions 262 are connected to the vacuum source 121 such as a vacuumpump via the fluid passages 37, 38 and valves V1, V2. When thecommunication holes 261 a, 262 a of the suction portions 261, 262 areconnected to the vacuum source 121, a negative pressure is developed atthe lower opening ends of the communication holes 261 a, 262 a thereofto attract a semiconductor wafer W to the lower ends of the innersuction portions 261 and the outer suction portions 262. The innersuction portions 261 and the outer suction portions 262 have elasticsheets 261 b, 262 b, such as thin rubber sheets, attached to their lowerends, for thereby elastically contacting and holding the semiconductorwafer W on the lower surfaces thereof.

Since there is a small gap G between the outer circumferential surfaceof the seal ring 204 and the inner circumferential surface of theretainer ring 3, the holder ring 205, the chucking plate 206, and theseal ring 204 attached to the chucking plate 206 can vertically be movedwith respect to the top ring body 2 and the retainer ring 3, and henceare of a floating structure with respect to the top ring body 2 and theretainer ring 3. The stopper 205 b of the holder ring 205 has aplurality of teeth 205 c projecting radially outwardly from the outercircumferential edge thereof. Downward movement of the members includingthe holder ring 205 is limited to a predetermined range by engaging theteeth 205 c with the upper surface of the radially inwardly projectingportion of the retainer ring 3.

Next, operation of the top ring 1 thus constructed will be described indetail below.

In the polishing apparatus constructed above, when a semiconductor waferW is to be delivered to the polishing apparatus, the top ring 1 as awhole is moved to a position to which the semiconductor wafer W istransferred, and the communication holes 261 a, 262 a of the innersuction portions 261 and the outer suction portions 262 are connectedvia the fluid passages 37, 38 to the vacuum source 121. Thesemiconductor wafer W is attracted under vacuum to the lower ends of theinner suction portions 261 and the outer suction portions 262 by suctioneffect of the communication holes 261 a, 262 a. With the semiconductorwafer W attracted to the top ring 1, the top ring 1 as a whole is movedto a position above the polishing table 100 having the polishing surface(polishing pad 101) thereon. The outer circumferential edge of thesemiconductor wafer W is held by the retainer ring 3 so that thesemiconductor wafer W is not removed from the top ring 1.

For polishing the semiconductor wafer W, the attraction of semiconductorwafer W by the suction portions 261, 262 is released, and thesemiconductor wafer W is held on the lower surface of the top ring 1.Simultaneously, the top ring air cylinder 111 connected to the top ringdrive shaft 11 is actuated to press the retainer ring 3 fixed to thelower end of the top ring 1 against the polishing surface on thepolishing table 100 under a predetermined pressure. In such a state,pressurized fluids are respectively supplied to the pressure chambers222, 223, the central pressure chamber 224, and the intermediatepressure chamber 225 under respective pressures, thereby pressing thesemiconductor wafer W against the polishing surface on the polishingtable 100. The polishing liquid supply nozzle 102 supplies a polishingliquid Q onto the polishing pad 101 in advance, so that the polishingliquid Q is held on the polishing pad 101. Thus, the semiconductor waferW is polished by the polishing pad 101 with the polishing liquid Q beingpresent between the (lower) surface, to be polished, of thesemiconductor wafer W and the polishing pad 101.

The local areas of the semiconductor wafer W that are positioned beneaththe pressure chambers 222, 223 are pressed against the polishing surfaceunder the pressures of the pressurized fluids supplied to the pressurechambers 222, 223. The local area of the semiconductor wafer W that ispositioned beneath the central pressure chamber 224 is pressed via theelastic membrane 281 of the central bag 208 against the polishingsurface under the pressure of the pressurized fluid supplied to thecentral pressure chamber 224. The local area of the semiconductor waferW that is positioned beneath the intermediate pressure chamber 225 ispressed via the elastic membrane 291 of the ring tube 209 against thepolishing surface under the pressure of the pressurized fluid suppliedto the intermediate pressure chamber 225.

Therefore, the polishing pressures acting on the respective local areasof the semiconductor wafer W can be adjusted independently bycontrolling the pressures of the pressurized fluids supplied to therespective pressure chambers 222 to 225. Specifically, the respectiveregulators R3 to R6 independently regulate the pressures of thepressurized fluids supplied to the pressure chambers 222 to 225 forthereby adjusting the pressing forces applied to press the local areasof the semiconductor wafer W against the polishing pad 101 on thepolishing table 100. With the polishing pressures on the respectivelocal areas of the semiconductor wafer W being adjusted independently todesired values, the semiconductor wafer W is pressed against thepolishing pad 101 on the polishing table 100 that is being rotated.Similarly, the pressure of the pressurized fluid supplied to the topring air cylinder 111 can be regulated by the regulator R1 to adjust theforce with which the retainer ring 3 presses the polishing pad 101.While the semiconductor wafer W is being polished, the force with whichthe retainer ring 3 presses the polishing pad 101 and the pressing forcewith which the semiconductor wafer W is pressed against the polishingpad 101 can appropriately be adjusted for thereby applying polishingpressures in a desired pressure distribution to a central area (C1 inFIG. 3), an inner area (C2) between the central area and an intermediatearea, the intermediate area (C3), a peripheral area (C4) of thesemiconductor wafer W, and a peripheral portion of the retainer ring 3which is positioned outside of the semiconductor wafer W.

In this manner, the semiconductor wafer W is divided into the fourconcentric circular and annular areas (C1 to C4), which can respectivelybe pressed under independent pressing forces. A polishing rate dependson a pressing force applied to a semiconductor wafer W against apolishing surface. As described above, since the pressing forces appliedto those areas can independently be controlled, the polishing rates ofthe four circular and annular areas (C1 to C4) of the semiconductorwafer W can independently be controlled. Consequently, even if thethickness of a thin film to be polished on the surface of thesemiconductor wafer W suffers radial variations, the thin film on thesurface of the semiconductor wafer W can be polished uniformly withoutbeing insufficiently or excessively polished over the entire surface ofthe semiconductor wafer. More specifically, even if the thickness of thethin film to be polished on the surface of the semiconductor wafer Wdiffers depending on the radial position on the semiconductor wafer W,the pressure in a pressure chamber positioned over a thicker area of thethin film is made higher than the pressure in other pressure chambers,or the pressure in a pressure chamber positioned over a thinner area ofthe thin film is made lower than the pressure in other pressurechambers. In this manner, the pressing force applied to the thicker areaof the thin film against the polishing surface is made higher than thepressing force applied to the thinner area of the thin film against thepolishing surface, thereby selectively increasing the polishing rate ofthe thicker area of the thin film. Consequently, the entire surface ofthe semiconductor wafer W can be polished exactly to a desired levelover the entire surface of the semiconductor wafer W irrespective of thefilm thickness distribution produced at the time the thin film isformed.

Any unwanted edge rounding on the circumferential edge of thesemiconductor wafer W can be prevented by controlling the pressing forceapplied to the retainer ring 3. If the thin film to be polished on thecircumferential edge of the semiconductor wafer W has large thicknessvariations, then the pressing force applied to the retainer ring 3 isintentionally increased or reduced to thus control the polishing rate ofthe circumferential edge of the semiconductor wafer W. When thepressurized fluids are supplied to the pressure chambers 222 to 225, thechucking plate 206 is subjected to upward forces. In the presentembodiment, the pressurized fluid is supplied to the pressure chamber221 via the fluid passage 31 to prevent the chucking plate 206 frombeing lifted under the forces due to the pressure chambers 222 to 225.

As described above, the pressing force applied by the top ring aircylinder 111 to press the retainer ring 3 against the polishing pad 101and the pressing forces applied by the pressurized air supplied to thepressure chambers 222 to 225 to press the local areas of thesemiconductor wafer W against the polishing pad 101 are appropriatelyadjusted to polish the semiconductor wafer W. When the polishing of thesemiconductor wafer W is finished, the semiconductor wafer W isattracted to the lower ends of the inner suction portions 261 and theouter suction portions 262 under vacuum in the same manner as describedabove. At this time, the supply of the pressurized fluids into thepressure chambers 222 to 225 to press the semiconductor wafer W againstthe polishing surface is stopped, and the pressure chambers 222 to 225are vented to the atmosphere. Accordingly, the lower ends of the innersuction portions 261 and the outer suction portions 262 are brought intocontact with the semiconductor wafer W. The pressure chamber 221 isvented to the atmosphere or evacuated to develop a negative pressuretherein. If the pressure chamber 221 is maintained at a high pressure,then the semiconductor wafer W is strongly pressed against the polishingsurface only in areas brought into contact with the inner suctionportions 261 and the outer suction portions 262. Therefore, it isnecessary to decrease the pressure in the pressure chamber 221immediately. Accordingly, a relief port 239 penetrating from thepressure chamber 221 through the top ring body 2 may be provided fordecreasing the pressure in the pressure chamber 221 immediately, asshown in FIG. 2. In this case, when the pressure chamber 221 ispressurized, it is necessary to continuously supply the pressurizedfluid into the pressure chamber 221 via the fluid passage 31. The reliefport 239 comprises a check valve for preventing an outside air fromflowing into the pressure chamber 221 at the time when a negativepressure is developed in the pressure chamber 221.

After attraction of the semiconductor wafer W, the top ring 1 as a wholeis moved to a position to which the semiconductor wafer W is to betransferred, and then a fluid (e.g., compressed air or a mixture ofnitrogen and pure water) is ejected to the semiconductor wafer W via thecommunication holes 261 a, 262 a of the inner suction portions 261 andthe outer suction portions 262 to release the semiconductor wafer W fromthe top ring 1.

The polishing liquid Q used to polish the semiconductor wafer W tends toflow through the small gap G between the outer circumferential surfaceof the seal ring 204 and the retainer ring 3. If the polishing liquid Qis firmly deposited in the gap G, then the holder ring 205, the chuckingplate 206, and the seal ring 204 are prevented from smoothly movingvertically with respect to the top ring body 2 and the retainer ring 3.To avoid such a drawback, a cleaning liquid (pure water) is suppliedthrough the fluid passage 32 to the cleaning liquid passage 251.Accordingly, the pure water is supplied via a plurality of communicationholes 253 to a region above the gap G, thus cleaning the gap G toprevent the polishing liquid Q from being firmly deposited in the gap G.The pure water should preferably be supplied after the polishedsemiconductor wafer W is released and until a next semiconductor waferto be polished is attracted to the top ring 1. It is also preferable todischarge all the supplied pure water out of the top ring 1 before thenext semiconductor wafer is polished, and hence to provide the retainerring 3 with a plurality of through-holes 3 a shown in FIG. 2.Furthermore, if a pressure buildup is developed in a space 226 definedbetween the retainer ring 3, the holder ring 205, and the pressurizingsheet 207, then it acts to prevent the chucking plate 206 from beingelevated in the top ring body 2. Therefore, in order to allow thechucking plate 206 to be elevated smoothly in the top ring body 2, thethrough-holes 3 a should preferably be provided for equalizing thepressure in the space 226 with the atmospheric pressure.

As described above, according to a substrate holding apparatus of thefirst embodiment, the pressures in the pressure chambers 222, 223, thepressure chamber 224 in the central bag 208, and the pressure chamber225 in the ring tube 209 are independently controlled to control thepressing forces acting on the semiconductor wafer W.

A first example of the ring tube 209 in the substrate holding apparatusaccording to the first embodiment of the present invention will bedescribed in detail below. Although only the ring tube 209 will bedescribed below, the following description can be applied to the centralbag 208.

FIG. 4 is a vertical cross-sectional view showing the ring tube 209shown in FIG. 2, and FIG. 5 is a vertical cross-sectional view showingthe elastic membrane 291 of the ring tube 209 shown in FIG. 4. As shownin FIGS. 4 and 5, the elastic membrane 291 of the ring tube 209 in thefirst example has an abutment portion 291 b having flanges 291 aprojecting outwardly, and connecting portions 291 c connected via thering tube holder 292 to the chucking plate 206. The connecting portions291 c extend upwardly from base portions 291 d of the flanges 291 a. Alower surface of the abutment portion 291 b is brought into contact withthe upper surface of the semiconductor wafer W. The flanges 291 a, theabutment portion 291 b, and the connecting portions 291 c are integrallymade of the same material.

As described above, when the semiconductor wafer is polished,pressurized fluids are supplied to the pressure chamber 222, and thepressure chamber 223 surrounding the ring tube 209. Thus, the flanges291 a are brought into close contact with the semiconductor wafer W bythe pressurized fluids supplied to the pressure chambers 222, 223.Accordingly, even if the pressure of the pressurized fluid supplied tothe pressure chamber 222 or 223 surrounding the pressure chamber 225 isconsiderably higher than the pressure of the pressurized fluid suppliedto the pressure chamber 225 defined in the ring tube 209, thehigh-pressure fluid surrounding the pressure chamber 225 is preventedfrom flowing into the lower portion of the ring tube 209. Therefore, theflanges 291 a can widen the range of pressure control in each of thepressure chambers, for thereby pressing the semiconductor wafer morestably.

Openings 291 e are formed in central portions of the abutment portion291 b of the ring tube 209, and thus a pressurized fluid supplied to theintermediate pressure chamber 225 directly contacts with the uppersurface of the semiconductor wafer W through the openings 291 e of theabutment portion 291 b. Since a pressurized fluid is supplied to theintermediate pressure chamber 225 during polishing, the pressurizedfluid presses the abutment portion 291 b of the ring tube 209 againstthe upper surface of the semiconductor wafer W. Therefore, even if theopenings 291 e are formed in the abutment portion 291 b, a pressurizedfluid in the intermediate pressure chamber 225 hardly flows out to theexterior of the intermediate pressure chamber 225. Further, when thesemiconductor wafer W is released, a downward pressure can be appliedthrough the openings 291 e to the semiconductor wafer W by a pressurizedfluid, so that the semiconductor wafer W can more smoothly be released.

When the pressurized fluid supplied to the intermediate pressure chamber225 is controlled in temperature and the temperature of thesemiconductor wafer W is controlled from the backside of the surface tobe polished, as described above, the openings 291 e formed in theabutment portion 291 b of the ring tube 209 can increase the area inwhich the pressurized fluid controlled in temperature is brought intocontact with the semiconductor wafer W. Therefore, controllability intemperature of the semiconductor wafer W can be improved. Further, whenthe polishing of the semiconductor wafer W is finished and thesemiconductor wafer W is released, the intermediate pressure chamber 225is opened to the outside air via the openings 291 e. Thus, the fluidsupplied into the intermediate pressure chamber 225 is prevented fromremaining in the intermediate pressure chamber 225. Therefore, even ifsemiconductor wafers W are continuously polished, controllability intemperature of the semiconductor wafer W can be maintained.

In a case where the aforementioned flanges 291 a are provided at theabutment portion 291 b of the ring tube 209, when a pressurized fluid issupplied to the pressure chamber 221 to press the chucking plate 206downwardly for polishing, downward forces may excessively be applied toportions of the semiconductor wafer W near the base portions 291 d ofthe flanges 291 a of the ring tube 209 by the connecting portions 291 c,so that a polishing rate may be locally increased at those portions.

On the other hand, as shown in FIGS. 6A through 6C, in a case where,after the semiconductor wafer W is brought into close contact with theabutment portion 291 b of the ring tube 209, the pressure chamber 221 issupplied with a pressure smaller than the sum of pressing forces appliedto the pressure chambers 222 to 225 to polish the semiconductor wafer insuch a state that the chucking plate 206 is lifted, upward forces may beapplied to portions near the base portions 291 d of the flanges 291 awhich is brought into close contact with the semiconductor wafer W bythe connecting portions 291 c. Thus, a vacuum 293 may be formed near thebase portions 291 d (see FIG. 6C), so that a polishing rate may belocally lowered at those portions.

In the above viewpoints, in the present embodiment, the connectingportions 291 c of the ring tube 209 are made of a soft material having ahigher flexibility than the abutment portion 291 b. With thisconfiguration, even if the chucking plate 206 is downwardly pressed forpolishing, excessive downward forces are not applied to thesemiconductor wafer W which is brought into close contact with theabutment portion 291 b because the connecting portions 291 c are likelyto be elastically deformed, so that a uniform polishing rate can beachieved over the entire surface of the abutment portion 291 b exceptthe flanges 291 a. Further, even if the chucking plate 206 is lifted forpolishing, excessive upward forces are not applied to the abutmentportion 291 b because the connecting portions 291 c are likely toextend. Thus, a vacuum is not formed near the base portions 291 d of theflanges 291 a, so that a uniform polishing rate can be achieved over theentire surface of the abutment portion 291 b except the flanges 291 a.Only a vertically extending portions 291 f (see FIG. 5) of theconnecting portions 291 c may be made of a soft material having a highflexibility, or, in addition thereto, portions 291 g held by the ringtube holder 292 may also be made of a soft material having a highflexibility.

FIG. 7 is a vertical cross-sectional view showing a second example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention. In the ring tube of the secondexample, the connecting portions 291 c have thin portions 294 having athickness smaller than the thickness of the abutment portion 291 b. Thethin portions 294 are constricted inwardly as shown in FIG. 7. With suchthin portions 294, even if the chucking plate 206 is pressed downwardlyfor polishing, excessive downward forces are not applied to thesemiconductor wafer W which is brought into close contact with theabutment portion 291 b because the connecting portions 291 c are likelyto be deformed at the thin portions 294, so that a uniform polishingrate can be achieved over the entire surface of the abutment portion 291b except the flanges 291 a. Further, even if the chucking plate 206 islifted for polishing, excessive upward forces are not applied to theabutment portion 291 b because the thin portions 294 are likely toextend. Thus, a vacuum is not formed near the base portions 291 d of theflanges 291 a, so that a uniform polishing rate can be achieved over theentire surface of the abutment portion 291 b except the flanges 291 a.Particularly, when the thin portions 294 are formed so as to beconstricted inwardly in a cross-section, the above effects caneffectively be achieved.

FIG. 8 is a vertical cross-sectional view showing a third example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention. In the ring tube of the thirdexample, intermediate members 295 having a low adhesiveness to thesemiconductor wafer W is attached to the lower surfaces of the baseportions 291 d of the flanges 291 a. Any members can be used as theintermediate member 295 as long as it has a low adhesiveness to thewafer W. For example, a cellophane tape may be used as the intermediatemember 295. The intermediate member 295 should preferably be as thin aspossible, and preferably have a thickness of 0.2 mm or smaller. Withthis arrangement, even if the chucking plate 206 is lifted forpolishing, a vacuum is unlikely to be formed near the base portions 291d of the flanges 291 a because the base portions 291 d of the flanges291 a are unlikely to be brought into close contact with thesemiconductor wafer W. Therefore, a uniform polishing rate can beachieved over the entire surface of the abutment portion 291 b exceptthe flanges 291 a. Instead of mounting such intermediate members 295,adhesiveness between the base portions 291 d of the flanges 291 a andthe semiconductor wafer W may be weakened, for example, by forming agroove in the lower surfaces of the base portions 291 d of the flanges291 a, or by forming the lower surfaces of the base portions 291 d asrough surfaces.

FIG. 9 is a vertical cross-sectional view showing a fourth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention. In the ring tube of the fourthexample, ring-like hard members 296 made of a material harder than theelastic membrane 291 (e.g., stainless) are embedded in the base portions291 d of the flanges 291 a. With this arrangement, even if the chuckingplate 206 is downwardly pressed for polishing, excessive downward forcesare not applied to the semiconductor wafer W which is brought into closecontact with the abutment portion 291 b because downward forces by theconnecting portions 291 c are dispersed by the hard members 296, so thata uniform polishing rate can be achieved over the entire surface of theabutment portion 291 b except the flanges 291 a. Further, even if thechucking plate 206 is lifted for polishing, a vacuum is not formed nearthe base portions 291 d of the flanges 291 a because the hard members296 prevent deformation of the vicinity of the base portions 291 d ofthe flanges 291 a. Therefore, a uniform polishing rate can be achievedover the entire surface of the abutment portion 291 b except the flanges291 a.

FIG. 10 is a vertical cross-sectional view showing a fifth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention. The fifth example corresponds to anexample of a ring tube in which a connecting portion 291 h positionedradially inwardly, i.e., near the center of the semiconductor wafer W,has a thickness smaller than a connecting portion 291 i positionedradially outwardly, in the elastic membrane 291 of the ring tube of thefirst example. Because a cylinder having a smaller curvature generallyhas a stiffness larger than a cylinder having a larger curvature, avertical force applied to the base portion of the flange by theconnecting portion positioned radially inwardly becomes larger than aforce applied to the base portion of the flange by the connectingportion positioned radially outwardly. Therefore, as shown in the fifthexample, when the connecting portion 291 h positioned radially inwardlyis thinner than the connecting portion 291 i positioned radiallyoutwardly, vertical forces applied to the base portions of the flangesby these connecting portions 291 h, 291 i can be adjusted to the samelevel, and a uniform polishing rate can be achieved over the entiresurface of the abutment portion 291 b except the flanges 291 a. When theconnecting portion positioned radially inwardly is made of a materialhaving a flexibility higher than the connecting portion positionedradially outwardly in the ring tube of the first example, the similareffects are expected.

FIG. 11 is a vertical cross-sectional view showing a sixth example of anelastic membrane of a ring tube in a substrate holding apparatusaccording to the present invention. The sixth example corresponds to anexample of a ring tube in which a flange 291 j projecting radiallyoutwardly has a length larger than a flange 291 k projecting radiallyinwardly, in the elastic membrane 291 of the ring tube of the firstexample. With this arrangement, a sealing capability can be enhanced atthe flange 291 j projecting radially outwardly, so that a uniformpolishing rate can be achieved over the entire surface of the abutmentportion 291 b except the flanges 291 a.

FIGS. 12A through 12C are vertical cross-sectional views showing aseventh example of a ring tube in a substrate holding apparatusaccording to the present invention. As shown in FIG. 12A, the elasticmembrane 391 of the ring tube of the seventh example has an abutmentportion 391 b having flanges 391 a projecting outwardly, extendingportions 391 d extending outwardly from base portions 391 c of theflanges 391 a to form grooves 392 between the extending portions 391 dand the flanges 391 a, and connecting portions 391 e connected via thering tube holder 292 to the chucking plate 206. The extending portions391 d extend outwardly from the base portions 391 c of the flanges 391 ato positions inward of tips of the flanges 391 a, and the connectingportions 391 e extend upwardly from outward ends of the extendingportions 391 d. The flanges 391 a, the abutment portion 391 b, theconnecting portions 391 e, and the extending portions 391 d areintegrally made of the same material. An opening 391 f is formed in acentral portion of the abutment portion 391 b.

With this arrangement, in a case where the chucking plate 206 is liftedfor polishing after the semiconductor wafer W is brought into closecontact with the abutment portion 391 b (see FIG. 12B), upward forces bythe connecting portions 391 e are converted into forces in horizontal oroblique directions by the extending portions 391 d, and the convertedforces are applied to the base portions 391 c of the flanges 391 a (seeFIG. 12C). Therefore, upward forces applied to the base portions 391 cof the flanges 391 a can be made extremely small, so that excessiveupward forces are not applied to the abutment portion 391 b.Accordingly, a vacuum is not formed near the base portions 391 d, sothat a uniform polishing rate can be achieved over the entire surface ofthe abutment portion 391 b except the flanges 391 a. In this case, thethickness of the connecting portions 391 e or the length of the flanges391 a maybe varied between the connecting portion disposed radiallyinwardly and the connecting portion disposed radially outwardy, as withthe ring tube in the fifth or sixth example. Further, the length of theextending portions 391 d may be varied between the extending portiondisposed radially inwardly and the extending portion disposed radiallyoutwardly. Furthermore, the thickness of the flanges 391 a may be variedaccording to the type of a film formed on the semiconductor wafer to bepolished or the polishing pad. When the resistance or the polishingtorque transmitted to the semiconductor wafer is large, the thickness ofthe flanges 391 a should preferably be made larger in order to preventtorsion of the flanges 391 a.

In the substrate holding apparatus according to the first embodimentdescribed above, the fluid passages 31, 33, 34, 35 and 36 are providedas separate passages. However, these fluid passages maybe combined witheach other, or the pressure chambers may be communicated with each otherin accordance with the magnitude of the pressing force to be applied tothe semiconductor wafer W and the position to which the pressing forceis applied. In the first embodiment, the central bag 208 and the ringtube 209 are brought into direct contact with the semiconductor wafer W.However, the present invention is not limited to such a configuration.For example, an elastic pad may be interposed between the central bag208 and ring tube 209 and the semiconductor wafer W so that the centralbag 208 and the ring tube 209 are brought into indirect contact with thesemiconductor wafer W. Further, the above examples may appropriately becombined with each other.

In the substrate holding apparatus according to the first embodimentdescribed above, the polishing surface is constituted by the polishingpad. However, the polishing surface is not limited to this. For example,the polishing surface may be constituted by a fixed abrasive. The fixedabrasive is formed into a flat plate comprising abrasive particles fixedby a binder. With the fixed abrasive for polishing, the polishingprocess is performed by the abrasive particles self-generated from thefixed abrasive. The fixed abrasive comprises abrasive particles, abinder, and pores. For example, cerium dioxide (CeO2) having an averageparticle diameter of 0.5 μm is used as an abrasive particle, and epoxyresin is used as a binder. Such a fixed abrasive forms a harderpolishing surface. The fixed abrasive includes a fixed abrasive padhaving a two-layer structure formed by a thin layer of a fixed abrasiveand an elastic polishing pad attached to a lower surface of the layer ofthe fixed abrasive. IC-1000 described above may be used for another hardpolishing surface.

As described above, according to the substrate holding apparatus of thefirst embodiment of the present invention, pressures to be applied tothe substrate can independently be controlled, and hence a pressingforce applied to a thicker area of a thin film can be made higher than apressing force applied to a thinner area of the thin film, therebyselectively increasing the polishing rate of the thicker area of thethin film. Thus, an entire surface of a substrate can be polishedexactly to a desired level irrespective of the film thicknessdistribution obtained at the time the thin film is formed. Further, evenif a vertically movable member is pressed downwardly for polishing,excessive downward forces are not applied to the substrate which isbrought into close contact with the abutment portion, so that a uniformpolishing rate can be achieved in an area between the base portions.Further, even if a vertically movable member is lifted for polishing,excessive upward forces are not applied to the abutment portion, so thata vacuum is not formed near the base portions of the flanges to achievea uniform polishing rate in an area between the base portions.

Next, a substrate holding apparatus according to a second embodiment ofthe present invention will be described below. FIG. 13 is a verticalcross-sectional view showing a top ring 1 as a substrate holdingapparatus according to the second embodiment of the present invention,and FIG. 14 is a bottom view showing the top ring 1 shown in FIG. 13. Asshown in FIG. 13, the top ring 1 constituting a substrate holdingapparatus comprises a top ring body 2 in the form of a cylindricalhousing with a receiving space defined therein, and a retainer ring 3fixed to the lower end of the top ring body 2. The top ring body 2 ismade of a material having high strength and rigidity, such as metal orceramics. The retainer ring 3 is made of highly rigid synthetic resin,ceramics, or the like.

The top ring body 2 comprises a cylindrical housing 2 a, an annularpressurizing sheet support 2 b fitted into the cylindrical portion ofthe housing 2 a, and an annular seal 2 c fitted over an outercircumferential edge of an upper surface of the housing 2 a. Theretainer ring 3 is fixed to the lower end of the housing 2 a of the topring body 2. The retainer ring 3 has a lower portion projecting radiallyinwardly. The retainer ring 3 may be formed integrally with the top ringbody 2.

A top ring drive shaft 11 is disposed above the central portion of thehousing 2 a of the top ring body 2, and the top ring body 2 is coupledto the top ring drive shaft 11 by a universal joint 10. The universaljoint 10 has a spherical bearing mechanism by which the top ring body 2and the top ring drive shaft 11 are tiltable with respect to each other,and a rotation transmitting mechanism for transmitting the rotation ofthe top ring drive shaft 11 to the top ring body 2. The sphericalbearing mechanism and the rotation transmitting mechanism transmit apressing force and a rotating force from the top ring drive shaft 11 tothe top ring body 2 while allowing the top ring body 2 and the top ringdrive shaft 11 to be tilted with respect to each other.

The spherical bearing mechanism comprises a hemispherical concave recess11 a defined centrally in the lower surface of the top ring drive shaft11, a hemispherical concave recess 2 d defined centrally in the uppersurface of the housing 2 a, and a bearing ball 12 made of a highly hardmaterial such as ceramics and interposed between the concave recesses 11a and 2 d. On the other hand, the rotation transmitting mechanismcomprises drive pins (not shown) fixed to the top ring drive shaft 11,and driven pins (not shown) fixed to the housing 2 a. Even if the topring body 2 is tilted with respect to the top ring drive shaft 11, thedrive pins and the driven pins remain in engagement with each otherwhile contact points are displaced because the drive pin and the drivenpin are vertically movable relatively to each other. Thus, the rotationtransmitting mechanism reliably transmits rotational torque of the topring drive shaft 11 to the top ring body 2.

The top ring body 2 and the retainer ring 3 secured to the top ring body2 have a space defined therein, which accommodates therein a seal ring404 having a lower surface brought into contact with a peripheralportion of the semiconductor wafer W held by the top ring 1, an annularholder ring 405, and a disk-shaped chucking plate 406 (verticallymovable member) which is vertically movable within the receiving spacein the top ring body 2.

The seal ring 404 has a radially outer edge clamped between the holderring 405 and the chucking plate 406 secured to the lower end of theholder ring 405 and extends radially inwardly so as to cover the lowersurface of the chucking plate 406 near its outer circumferential edge.The lower end surface of the seal ring 404 is brought into contact withthe upper surface of the semiconductor wafer W to be polished. The sealring 404 is made of a highly strong and durable rubber material such asethylene propylene rubber (EPDM), polyurethane rubber, or siliconerubber. The semiconductor wafer W has a recess defined in an outer edgethereof, which is referred to as a notch or orientation flat, forrecognizing (identifying) the orientation of the semiconductor wafer.The seal ring 404 should preferably extend radially inwardly of thechucking plate 406 from the innermost position of such as a notch ororientation flat.

A pressurizing sheet 407 comprising an elastic membrane extends betweenthe holder ring 405 and the top ring body 2. The pressurizing sheet 407has a radially outer edge clamped between the housing 2 a and thepressurizing sheet support 2 b of the top ring body 2, and a radiallyinner edge clamped between an upper end portion 405 a and a stopper 405b of the holder ring 405. The top ring body 2, the chucking plate 406,the holder ring 405, and the pressurizing sheet 407 jointly define apressure chamber 421 in the top ring body 2. As shown in FIG. 13, afluid passage 31 comprising tubes and connectors communicates with thepressure chamber 421, which is connected to a compressed air source 120via a regulator R2 provided on the fluid passage 31. The pressurizingsheet 407 is made of a highly strong and durable rubber material such asethylene propylene rubber (EPDM), polyurethane rubber, or siliconerubber.

In the case where the pressurizing sheet 407 is made of an elasticmaterial such as rubber, if the pressurizing sheet 407 is fixedlyclamped between the retainer ring 3 and the top ring body 2, then adesired horizontal surface cannot be maintained on the lower surface ofthe retainer ring 3 because of elastic deformation of the pressurizingsheet 407 as an elastic material. In order to prevent such a drawback,the pressurizing sheet 407 is clamped between the housing 2 a of the topring body 2 and the pressurizing sheet support 2 b provided as aseparate member in the present embodiment. The retainer ring 3 mayvertically be movable with respect to the top ring body 2, or theretainer ring 3 may have a structure capable of pressing the polishingsurface independently of the top ring body 2. In such cases, thepressurizing sheet 407 is not necessarily fixed in the aforementionedmanner.

A cleaning liquid passage 451 in the form of an annular groove isdefined in the upper surface of the housing 2 a near its outercircumferential edge over which the seal 2 c of the top ring body 2 isfitted. The cleaning liquid passage 451 communicates with a fluidpassage 32 via a through-hole 452, and is supplied with a cleaningliquid (pure water) via the fluid passage 32. A plurality ofcommunication holes 453 are defined in the housing 2 a and thepressurizing sheet support 2 b in communication with the cleaning liquidpassage 451. The communication holes 453 communicate with a small gap Gdefined between the outer circumferential surface of the seal ring 404and the inner circumferential surface of the retainer ring 3.

The chucking plate 406 has a central port 408 provided on a lowersurface of a central portion of the chucking plate 406, with an opening408 a defined at a central portion of the central port 408. A ring tube409 which serves as an abutment member brought into contact with thesemiconductor wafer W is mounted in a space defined between the chuckingplate 406 and the semiconductor wafer W. In the present embodiment, asshown in FIGS. 13 and 14, the ring tube 409 is disposed radiallyoutwardly of the central port 408 in surrounding relation thereto. Thechucking plate 406 has suction portions 440 extended downwardly therefrom outside of the ring tube 409. In the present embodiment, sixsuction portions 440 are provided.

The ring tube 409 comprises an elastic membrane 491 brought into contactwith the upper surface of the semiconductor wafer W, and a ring tubeholder 492 for detachably holding the elastic membrane 491 in position.The ring tube 409 has a pressure chamber 422 defined therein by theelastic membrane 491 and the ring tube holder 492. The space definedbetween the chucking plate 406 and the semiconductor wafer W is dividedinto a plurality of spaces by the ring tube 409. Accordingly, a pressurechamber 423 is defined radially inwardly of the ring tube 409, i.e.,around the central port 408, and a pressure chamber 424 is definedradially outwardly of the ring tube 409, i.e., around the suctionportions 440. The elastic membrane 491 of the ring tube 409 is made of ahighly strong and durable rubber material such as ethylene propylenerubber (EPDM), polyurethane rubber, or silicone rubber, as with thepressurizing sheet 407.

A fluid passage 33 comprising tubes and connectors communicates with thepressure chamber 422 in the ring tube 409. The pressure chamber 422 isconnected to the compressed air source 120 via a regulator R3 connectedto the fluid passages 33. A fluid passage 34 comprising tubes andconnectors communicates with the opening 408 a of the central port 408.The central port 408 is connected to the compressed air source 120 via aregulator R4 connected to the fluid passages 34. The suction portion 440has a communication hole 440 a communicating with a fluid passage 35comprising tubes and connectors. The suction portions 440 are connectedto the compressed air source 120 via a regulator R5 connected to thefluid passages 35. The compressed air source 120 develops a negativepressure at the opening ends of the communication holes 440 a of thesuction portions 440 to attract a semiconductor wafer W to the suctionportions 440. The suction portions 440 have elastic sheets 440 b, suchas thin rubber sheets, attached to their lower ends, for therebyelastically contacting and holding the semiconductor wafer Won the lowersurfaces thereof. The pressure chambers 421 to 424 are connected to therespective regulators R2 to R5 through a rotary joint (not shown)mounted on the upper end of the top ring shaft 110.

The pressure chamber 421 above the chucking plate 406 and the pressurechambers 422, 423, 424 are supplied with pressurized fluids such aspressurized air or atmospheric air or evacuated, via the fluid passages31, 33, 34 and 35 connected to the respective pressure chambers. Asshown in FIG. 1, the regulators R2 to R5 connected to the fluid passages31, 33, 34 and 35 of the pressure chambers 421 to 424 can respectivelyregulate the pressures of the pressurized fluids supplied to therespective pressure chambers. Thus, it is possible to independentlycontrol the pressures in the pressure chambers 421 to 424 orindependently introduce atmospheric air or vacuum into the pressurechambers 421 to 424. In this manner, the pressures in the pressurechambers 421 to 424 are independently varied with the regulators R2 toR5, so that the pressing forces to press the semiconductor wafer Wagainst the polishing pad 101 can be adjusted in local areas of thesemiconductor wafer W.

In this case, the pressurized fluid or the atmospheric air supplied tothe pressure chambers 422 to 424 may independently be controlled intemperature. With this configuration, it is possible to directly controlthe temperature of a workpiece such as a semiconductor wafer from thebackside of the surface to be polished. Particularly, when each of thepressure chambers is independently controlled in temperature, the rateof chemical reaction can be controlled in the chemical polishing processof CMP.

Since there is a small gap G between the outer circumferential surfaceof the seal ring 404 and the inner circumferential surface of theretainer ring 3, the holder ring 405, the chucking plate 406, and theseal ring 404 attached to the chucking plate 406 can vertically be movedwith respect to the top ring body 2 and the retainer ring 3, and henceare of a floating structure with respect to the top ring body 2 and theretainer ring 3. The stopper 405 b of the holder ring 405 has aplurality of teeth 405 c projecting radially outwardly from the outercircumferential edge thereof. Downward movement of the members includingthe holder ring 405 is limited to a predetermined range by engaging theteeth 405 c with the upper surface of the radially inwardly projectingportion of the retainer ring 3.

For example, in a case where the chucking plate is made of PPS(polyphenylene sulfide), if the pressure in the pressure chamber 421 ishigher than the pressures in the pressure chambers 422 to 424 below thechucking plate 406, the chucking plate is bent so that the suctionportions 440 press the semiconductor wafer W to increase polishing ratesat those local areas. Accordingly, the chucking plate 406 in the presentembodiment is made of a material having a larger stiffness and a lighterweight than PPS, e.g., epoxy resin, preferably a fiber reinforcedmaterial such as a glass fiber reinforced material. Thus, with thechucking plate 406 made of a material having a large stiffness, even ifthe pressure in the pressure chamber 421 is higher than the pressures inthe pressure chambers 422 to 424 below the chucking plate 406, thechucking plate 406 becomes unlikely to be bent, so that polishing ratesare prevented from being locally increased. Particularly, since epoxyresin has no magnetism, it is suitable for cases where the filmthickness of a thin film formed on a surface of a semiconductor wafer ismeasured with a film thickness method using eddy current in such a statethat the semiconductor wafer to be polished is held by a top ring. Thematerial is not limited to epoxy resin, and it is also effective to useother resin having a large stiffness, fiber reinforced materialsthereof, or ceramics.

Next, operation of the top ring 1 thus constructed will be described indetail below.

In the polishing apparatus constructed above, when a semiconductor waferW is to be delivered to the polishing apparatus, the top ring 1 as awhole is moved to a position to which the semiconductor wafer W istransferred, and the communication holes 440 a of the suction portions440 are connected via the fluid passage 35 to the vacuum source 121. Thesemiconductor wafer W is attracted under vacuum to the lower ends of thesuction portions 440 by suction effect of the communication holes 440 a.With the semiconductor wafer W attracted to the top ring 1, the top ring1 as a whole is moved to a position above the polishing table 100 havingthe polishing surface (polishing pad 101) thereon. The outercircumferential edge of the semiconductor wafer W is held by theretainer ring 3 so that the semiconductor wafer W is not removed fromthe top ring 1.

For polishing the semiconductor wafer W, the attraction of semiconductorwafer W by the suction portions 440 is released, and the semiconductorwafer W is held on the lower surface of the top ring 1. Simultaneously,the top ring air cylinder 111 connected to the top ring drive shaft 11is actuated to press the retainer ring 3 fixed to the lower end of thetop ring 1 against the polishing surface on the polishing table 100under a predetermined pressure. In such a state, pressurized fluids arerespectively supplied to the pressure chamber 422, 423, 424 underrespective pressures, thereby pressing the semiconductor wafer W againstthe polishing surface on the polishing table 100. The polishing liquidsupply nozzle 102 supplies a polishing liquid Q onto the polishing pad101 in advance, so that the polishing liquid Q is held on the polishingpad 101. Thus, the semiconductor wafer W is polished by the polishingpad 101 with the polishing liquid Q being present between the (lower)surface, to be polished, of the semiconductor wafer W and the polishingpad 101.

The local areas of the semiconductor wafer W that are positioned beneaththe pressure chambers 423, 424 are pressed against the polishing surfaceunder the pressures of the pressurized fluids supplied to the pressurechambers 423, 424. The local area of the semiconductor wafer W that ispositioned beneath the central pressure chamber 422 is pressed via theelastic membrane 491 of the ring tube 409 against the polishing surfaceunder the pressure of the pressurized fluid supplied to the pressurechamber 422. Therefore, the polishing pressures acting on the respectivelocal areas of the semiconductor wafer W can be adjusted independentlyby controlling the pressures of the pressurized fluids supplied to therespective pressure chambers 422 to 424. Specifically, the respectiveregulators R3 to R5 independently regulate the pressures of thepressurized fluids supplied to the pressure chambers 422 to 424 forthereby adjusting the pressing forces applied to press the local areasof the semiconductor wafer W against the polishing pad 101 on thepolishing table 100. With the polishing pressures on the respectivelocal areas of the semiconductor wafer W being adjusted independently todesired values, the semiconductor wafer W is pressed against thepolishing pad 101 on the polishing table 100 that is being rotated.Similarly, the pressure of the pressurized fluid supplied to the topring air cylinder 111 can be regulated by the regulator R1 to adjust theforce with which the retainer ring 3 presses the polishing pad 101.While the semiconductor wafer W is being polished, the force with whichthe retainer ring 3 presses the polishing pad 101 and the pressing forcewith which the semiconductor wafer W is pressed against the polishingpad 101 can appropriately be adjusted for thereby applying polishingpressures in a desired pressure distribution to a central area (C1 inFIG. 14), an intermediate area (C2), a peripheral area (C3), and aperipheral portion of the retainer ring 3 which is positioned outside ofthe semiconductor wafer W.

In this manner, the semiconductor wafer W is divided into the threeconcentric circular and annular areas (C1 to C3), which can respectivelybe pressed under independent pressing forces. A polishing rate dependson a pressing force applied to a semiconductor wafer W against apolishing surface. As described above, since the pressing forces appliedto those areas can independently be controlled, the polishing rates ofthe three circular and annular areas (C1 to C3) of the semiconductorwafer W can independently be controlled. Consequently, even if thethickness of a thin film to be polished on the surface of thesemiconductor wafer W suffers radial variations, the thin film on thesurface of the semiconductor wafer W can be polished uniformly withoutbeing insufficiently or excessively polished over the entire surface ofthe semiconductor wafer. More specifically, even if the thickness of thethin film to be polished on the surface of the semiconductor wafer Wdiffers depending on the radial position on the semiconductor wafer W,the pressure in a pressure chamber positioned over a thicker area of thethin film is made higher than the pressure in other pressure chambers,or the pressure in a pressure chamber positioned over a thinner area ofthe thin film is made lower than the pressure in other pressurechambers. In this manner, the pressing force applied to the thicker areaof the thin film against the polishing surface is made higher than thepressing force applied to the thinner area of the thin film against thepolishing surface, thereby selectively increasing the polishing rate ofthe thicker area of the thin film. Consequently, the entire surface ofthe semiconductor wafer W can be polished exactly to a desired levelover the entire surface of the semiconductor wafer W irrespective of thefilm thickness distribution produced at the time the thin film isformed.

Any unwanted edge rounding on the circumferential edge of thesemiconductor wafer W can be prevented by controlling the pressing forceapplied to the retainer ring 3. If the thin film to be polished on thecircumferential edge of the semiconductor wafer W has large thicknessvariations, then the pressing force applied to the retainer ring 3 isintentionally increased or reduced to thus control the polishing rate ofthe circumferential edge of the semiconductor wafer W. When thepressurized fluids are supplied to the pressure chambers 422 to 424, thechucking plate 406 is subjected to upward forces. In the presentembodiment, the pressurized fluid is supplied to the pressure chamber421 via the fluid passage 31 to prevent the chucking plate 406 frombeing lifted under the forces due to the pressure chambers 422 to 424.

As described above, the pressing force applied by the top ring aircylinder 111 to press the retainer ring 3 against the polishing pad 101and the pressing forces applied by the pressurized air supplied to thepressure chambers 422 to 424 to press the local areas of thesemiconductor wafer W against the polishing pad 101 are appropriatelyadjusted to polish the semiconductor wafer W. When the polishing of thesemiconductor wafer W is finished, the semiconductor wafer W isattracted again to the lower ends of the suction portions 440 undervacuum. At this time, the supply of the pressurized fluids into thepressure chambers 422 to 424 to press the semiconductor wafer W againstthe polishing surface is stopped, and the pressure chambers 422 to 424are vented to the atmosphere. Accordingly, the lower ends of the suctionportions 440 are brought into contact with the semiconductor wafer W.The pressure chamber 421 is vented to the atmosphere or evacuated todevelop a negative pressure therein. If the pressure chamber 421 ismaintained at a high pressure, then the semiconductor wafer W isstrongly pressed against the polishing surface only in areas broughtinto contact with the suction portions 440.

After attraction of the semiconductor wafer W, the top ring 1 as a wholeis moved to a position to which the semiconductor wafer W is to betransferred, and then a fluid (e.g., compressed air or a mixture ofnitrogen and pure water) is ejected to the semiconductor wafer W via thecommunication holes 440 a of the suction portions 440 to release thesemiconductor wafer W from the top ring 1.

The polishing liquid Q used to polish the semiconductor wafer W tends toflow through the small gap G between the outer circumferential surfaceof the seal ring 404 and the retainer ring 3. If the polishing liquid Qis firmly deposited in the gap G, then the holder ring 405, the chuckingplate 406, and the seal ring 404 are prevented from smoothly movingvertically with respect to the top ring body 2 and the retainer ring 3.To avoid such a drawback, a cleaning liquid (pure water) is suppliedthrough the fluid passage 32 to the cleaning liquid passage 451.Accordingly, the pure water is supplied via a plurality of communicationholes 453 to a region above the gap G, thus cleaning the gap G toprevent the polishing liquid Q from being firmly deposited in the gap G.The pure water should preferably be supplied after the polishedsemiconductor wafer W is released and until a next semiconductor waferto be polished is attracted to the top ring 1. It is also preferable todischarge all the supplied pure water out of the top ring 1 before thenext semiconductor wafer is polished, and hence to provide the retainerring 3 with a plurality of through-holes 3 a shown in FIG. 13.Furthermore, if a pressure buildup is developed in a space 425 definedbetween the retainer ring 3, the holder ring 405, and the pressurizingsheet 407, then it acts to prevent the chucking plate 406 from beingelevated in the top ring body 2. Therefore, in order to allow thechucking plate 406 to be elevated smoothly in the top ring body 2, thethrough-holes 3 a should preferably be provided for equalizing thepressure in the space 425 with the atmospheric pressure.

As described above, according to a substrate holding apparatus of thesecond embodiment, the pressures in the pressure chambers 422, 423, 424are independently controlled to control the pressing forces acting onthe semiconductor wafer W.

The ring tube 409 of the substrate holding apparatus according to thesecond embodiment of the present invention will be described in detailbelow.

FIG. 15 is a vertical cross-sectional view showing the ring tube 409shown in FIG. 13. As shown in FIG. 15, the elastic membrane 491 of thering tube 409 in the present embodiment has an abutment portion 491 bhaving flanges 491 a projecting outwardly, and connecting portions 491 cconnected via the ring tube holder 492 to the chucking plate 406. Theconnecting portions 491 c extend upwardly from the base portions 491 dof the flanges 491 a. A lower surface of the abutment portion 491 b isbrought into contact with the upper surface of the semiconductor waferW. The flanges 491 a, the abutment portion 491 b, and the connectingportions 491 c are integrally made of the same material.

As described above, when the semiconductor wafer is polished,pressurized fluids are supplied to the pressure chamber 422, and thepressure chambers 423, 424 surrounding the ring tube 409. Thus, theflanges 491 a are brought into close contact with the semiconductorwafer W by the pressurized fluids supplied to the pressure chambers 423,424. Accordingly, even if the pressure of the pressurized fluid suppliedto the pressure chamber 423 or 424 surrounding the pressure chamber 422is considerably higher than the pressure of the pressurized fluidsupplied to the pressure chamber 422 defined in the ring tube 409, thehigh-pressure fluid surrounding the pressure chamber 422 is preventedfrom flowing into the lower portion of the ring tube 409. Therefore, theflanges 491 a can widen the range of pressure control in each of thepressure chambers, for thereby pressing the semiconductor wafer morestably.

Openings 491 e are formed at a plurality of central portions of theabutment portion 491 b of the ring tube 409, and thus a pressurizedfluid supplied to the pressure chamber 422 directly contacts with theupper surface of the semiconductor wafer W through the openings 491 e ofthe abutment portion 491 b. Since a pressurized fluid is supplied to thepressure chamber 422 during polishing, the pressurized fluid presses theabutment portion 491 b of the ring tube 409 against the upper surface ofthe semiconductor wafer W. Therefore, even if the openings 491 e areformed in the abutment portion 491 b, a pressurized fluid in thepressure chamber 422 hardly flows out to the exterior of the pressurechamber 422. Further, when the semiconductor wafer W is released, adownward pressure can be applied through the openings 491 e to thesemiconductor wafer W by a pressurized fluid, so that the semiconductorwafer W can more smoothly be released.

When the pressurized fluid supplied to the intermediate pressure chamber422 is controlled in temperature and the temperature of thesemiconductor wafer W is controlled from the backside of the surface tobe polished, as described above, the openings 491 e formed in theabutment portion 491 b of the ring tube 409 can increase the area inwhich the pressurized fluid controlled in temperature is brought intocontact with the semiconductor wafer W. Therefore, controllability intemperature of the semiconductor wafer W can be improved. Further, whenthe polishing of the semiconductor wafer W is finished and thesemiconductor wafer W is released, the pressure chamber 422 is opened tothe outside air via the openings 491 e. Thus, the fluid supplied intothe pressure chamber 4225 is prevented from remaining in the pressurechamber 422. Therefore, even if semiconductor wafers W are continuouslypolished, controllability in temperature of the semiconductor wafer Wcan be maintained.

As shown in FIG. 15, the chucking plate 406 has support portions 406 afor supporting the flanges 491 a of the ring tube 409. If the chuckingplate 406 has no support portions 406 a, then the flanges 491 a may bedeformed and attached to the lower surface of the chucking plate 406 asshown in FIG. 16 when pressurized fluids are supplied to the pressurechambers 423, 424 surrounding the ring tube 409. In such a state, it isimpossible to properly control the pressures of the pressure chambers422 to 424. Accordingly, in the present embodiment, the support portions406 a are provided on the chucking plate 406 for supporting the flanges491 a of the ring tube 409, as described above, to prevent the flanges491 a from being attached to the lower surface of the chucking plate 406and to stabilize the pressures of the pressure chambers 422 to 424. Inthis case, when the support portions have radial lengths larger than theradial lengths of the flanges 491 a, it is possible to support theflanges 491 a more reliably.

In this case, the flanges 491 a of the ring tube 409 are brought intocontact with the support portions 406 a of the chucking plate 406. Inorder to enhance adhesiveness of the flanges 491 a to the semiconductorwafer W, it is necessary to press the flanges 491 a by pressurizedfluids supplied to the pressure chambers 423, 424. Accordingly, in thepresent embodiment, as shown in FIG. 17, fluid introduction grooves 406b are formed in the support portions 406 a of the chucking plate 406 forstably pressing the flanges 491 a by pressurized fluids supplied to thepressure chambers 423, 424 to enhance adhesiveness between the flanges491 a and the semiconductor wafer W.

Similarly, with respect to the seal ring 404, the seal ring 404 may beattached to a peripheral portion of the chucking plate 406 by apressurized fluid supplied to the pressure chamber 424, as shown in FIG.18. Accordingly, in the present embodiment, a support portion 406 c isprovided at the peripheral portion of the chucking plate 406 forsupporting the seal ring 404, as shown in FIG. 19. In this case, as withthe support portions 406 a, fluid introduction grooves may be formed inthe support portion 406 c for stably pressing the seal ring 404 by apressurized fluid supplied to the pressure chamber 424 to enhanceadhesiveness between the seal ring 404 and the semiconductor wafer W.Further, since such grooves can introduce the pressurized fluid to theoutermost portion of the semiconductor wafer, a uniform pressing forcecan be achieved at the peripheral portion of the wafer.

When the retainer ring 3 is pressed against the polishing pad 101, thepolishing pad 101 may be raised (rebounded) near the retainer ring 3 sothat a polishing rate is locally increased at the peripheral portion ofthe semiconductor wafer W. In the present embodiment, the radial lengthd of the support portion 406 c of the chucking plate 406 is shortened toprevent the semiconductor wafer W from being excessively polished at theperipheral portion thereof. When the effects of the rebound are small,the length d is shortened to concentrate the pressing forces, or thelength d is lengthened to disperse the pressing forces, for varyingpolishing rates. Specifically, the length d is varied in a range of 1 mmto 7 mm to achieve desired polishing rates.

In the substrate holding apparatus according to the second embodimentdescribed above, the fluid passages 31, 33, 34 and 35 are provided asseparate passages. However, these fluid passages may be combined witheach other, or the pressure chambers may be communicated with each otherin accordance with the magnitude of the pressing force to be applied tothe semiconductor wafer W and the position to which the pressing forceis applied. In the above embodiment, the ring tube 409 is brought intodirect contact with the semiconductor wafer W. However, the presentinvention is not limited to such a configuration. For example, anelastic pad may be interposed between the ring tube 409 and thesemiconductor wafer W so that the ring tube 409 is brought into indirectcontact with the semiconductor wafer W.

In the second embodiment shown in FIGS. 13 through 19, the polishingsurface is constituted by the polishing pad. However, the polishingsurface is not limited to this. The polishing surface may be constitutedby a fixed abrasive as described in the first embodiment shown in FIGS.2 through 12.

As described above, according to the substrate holding apparatus of thesecond embodiment of the present invention, pressures to be applied tothe substrate can independently be controlled, and hence a pressingforce applied to a thicker area of a thin film can be made higher than apressing force applied to a thinner area of the thin film, therebyselectively increasing the polishing rate of the thicker area of thethin film. Thus, an entire surface of a substrate can be polishedexactly to a desired level irrespective of the film thicknessdistribution obtained at the time the thin film is formed. Further, witha vertically movable member made of a material having a large stiffnessand a light weight, e.g., epoxy resin, the vertically movable memberbecomes unlikely to be bent, so that polishing rates are prevented frombeing locally increased. Further, when a material having no magnetism isselected as a material of the vertically movable member, it is suitablefor cases where the film thickness of a thin film formed on a surface ofa semiconductor wafer is measured with a film thickness method usingeddy current in such a state that the semiconductor wafer to be polishedis held by a top ring.

Next, a substrate holding apparatus according to a third embodiment ofthe present invention will be described below. FIG. 20 is a verticalcross-sectional view showing a top ring 1 according to the thirdembodiment of the present invention. As shown in FIG. 20, the top ring 1constituting a substrate holding apparatus comprises a top ring body 2in the form of a cylindrical housing with a receiving space definedtherein, and a retainer ring 3 fixed to the lower end of the top ringbody 2. The top ring body 2 is made of a material having high strengthand rigidity, such as metal or ceramics. The retainer ring 3 is made ofhighly rigid synthetic resin, ceramics, or the like.

The top ring body 2 comprises a cylindrical housing 2 a, an annularpressurizing sheet support 2 b fitted into the cylindrical portion ofthe housing 2 a, and an annular seal 2 c fitted over an outercircumferential edge of an upper surface of the housing 2 a. Theretainer ring 3 is fixed to the lower end of the housing 2 a of the topring body 2. The retainer ring 3 has a lower portion projecting radiallyinwardly. The retainer ring 3 may be formed integrally with the top ringbody 2.

A top ring drive shaft 11 is disposed above the central portion of thehousing 2 a of the top ring body 2, and the top ring body 2 is coupledto the top ring drive shaft 11 by a universal joint 10. The universaljoint 10 has a spherical bearing mechanism by which the top ring body 2and the top ring drive shaft 11 are tiltable with respect to each other,and a rotation transmitting mechanism for transmitting the rotation ofthe top ring drive shaft 11 to the top ring body 2. The sphericalbearing mechanism and the rotation transmitting mechanism transmit apressing force and a rotating force from the top ring drive shaft 11 tothe top ring body 2 while allowing the top ring body 2 and the top ringdrive shaft 11 to be tilted with respect to each other.

The top ring body 2 and the retainer ring 3 secured to the top ring body2 have a space defined therein, which accommodates therein an edge bag504 having a lower surface brought into contact with a peripheralportion of the semiconductor wafer W held by the top ring 1, an holderring 505, a disk-shaped chucking plate 506 which is vertically movablewithin the receiving space in the top ring body 2, and a torquetransmitting member 507 having a lower surface brought into contact withthe semiconductor wafer W at a radially inward position of the edge bag504.

The chucking plate 506 may be made of metal. However, when the thicknessof a thin film formed on a surface of a semiconductor wafer is measuredby a method using eddy current in such a state that the semiconductorwafer to be polished is held by the top ring, the chucking plate 506should preferably be made of a non-magnetic material, e.g., aninsulating material such as fluororesin or ceramics.

A pressurizing sheet 508 comprising an elastic membrane extends betweenthe holder ring 505 and the top ring body 2. The pressurizing sheet 508has a radially outer edge clamped between the housing 2 a and thepressurizing sheet support 2 b of the top ring body 2, and a radiallyinner edge clamped between an upper end portion 505 a and a stopper 505b of the holder ring 505. The top ring body 2, the chucking plate 506,the holder ring 505, and the pressurizing sheet 508 jointly define apressure chamber 521 in the top ring body 2. As shown in FIG. 20, afluid passage 31 comprising tubes and connectors communicates with thepressure chamber 521, which is connected to a compressed air source 120via a regulator R2 provided on the fluid passage 31. The pressurizingsheet 508 is made of a highly strong and durable rubber material such asethylene propylene rubber (EPDM), polyurethane rubber, or siliconerubber.

A cleaning liquid passage 551 in the form of an annular groove isdefined in the upper surface of the housing 2 a near its outercircumferential edge over which the seal 2 c of the top ring body 2 isfitted. The cleaning liquid passage 551 communicates with a fluidpassage 32 via a through-hole formed in the seal 2 c, and is suppliedwith a cleaning liquid (pure water) via the fluid passage 32. Aplurality of communication holes 553 a redefined in the housing 2 a andthe pressurizing sheet support 2 b in communication with the cleaningliquid passage 551. The communication holes 553 communicate with a smallgap G defined between the outer circumferential surface of the edge bag504 and the inner circumferential surface of the retainer ring 3.

FIG. 21 is a partial cross-sectional view showing the edge bag 504 ofFIG. 20. As shown in FIG. 21, the edge bag 504 has a radially outer edgeclamped between a stopper 505 b of the holder ring 505 and an edge bagholder 506 a disposed below the holder ring 505, and a radially inneredge clamped between the edge bag holder 506 a and a chucking plate body506 b. The lower end surface of the edge bag 504 is brought into contactwith a peripheral portion of the semiconductor wafer W to be polished.The edge bag 504 comprises an elastic membrane made of a highly strongand durable rubber material such as ethylene propylene rubber (EPDM),polyurethane rubber, or silicone rubber.

The lower surface of the edge bag 504 is brought into contact with theperipheral portion of the semiconductor wafer W and provided with aflange 541 projecting radially inwardly. The edge bag 504 has a (first)pressure chamber 522 defined therein by the elastic membrane. A fluidpassage 33 comprising tubes and connectors communicates with thepressure chamber 522. The pressure chamber 522 is connected to thecompressed air source 120 via a regulator R3 connected to the fluidpassages 33.

Upon polishing, the semiconductor wafer W is rotated in accordance withrotation of the top ring 1. Since the aforementioned edge bag 504 has asmall contact area with the semiconductor wafer W, rotational torque mayfails to completely be transmitted to the semiconductor wafer W.Accordingly, the torque transmitting member 507 is secured to thechucking plate 506 for transmitting sufficient torque to thesemiconductor wafer W by abutment with the semiconductor wafer W. Thetorque transmitting member 507 is in the form of an annular bag and isbrought into contact with the semiconductor wafer W with a contact arealarge enough to transmit sufficient torque to the semiconductor wafer W.

FIG. 22 is a partial cross-sectional view showing the torquetransmitting member 507 of FIG. 20. As shown in FIG. 22, the torquetransmitting member 507 comprises an elastic membrane 571 brought intocontact with the upper surface of the semiconductor wafer W, and atorque transmitting member holder 572 for detachably holding the elasticmembrane 571 in position. The torque transmitting member 507 has a space560 defined therein by the elastic membrane 571 and the torquetransmitting member holder 572. The elastic membrane 571 of the torquetransmitting member 507 is made of a highly strong and durable rubbermaterial such as ethylene propylene rubber (EPDM), polyurethane rubber,or silicone rubber, as with the edge bag 504.

As shown in FIG. 22, the elastic membrane 571 of the torque transmittingmember 507 has an abutment portion 571 b having flanges 571 a projectingoutwardly, and connecting portions 571 c connected via the torquetransmitting member holder 572 to the chucking plate 506. The connectingportions 571 c extend upwardly from the base portions 571 d of theflanges 571 a. A lower surface of the abutment portion 571 b is broughtinto contact with the upper surface of the semiconductor wafer W. Theconnecting portions 571 c have a plurality of communication holes 573provided at radially inward and outward positions, and the interior ofthe internal space 560 of the torque transmitting member 507 iscommunicated with external spaces 561, 562.

When the two connecting portions 571 c extending vertically are arrangedat relatively near positions, the connecting portions 571 c havesufficient strength to transmit torque. With the flanges 571 a, it ispossible to maintain a contact area with the semiconductor wafer W.

The space defined between the chucking plate 506 and the semiconductorwafer W is divided into a plurality of spaces, i.e., a pressure chamber522 disposed radially inwardly of the edge bag 504, the space 560 in thetorque transmitting member 507, a space 561 between the edge bag 504 andthe torque transmitting member 507, and a space 562 disposed radiallyinwardly of the torque transmitting member 507. As described above, thecommunication holes 573 are provided in the connecting portions 571 c ofthe torque transmitting member 507. Accordingly, the space 561, thespace 560, and the space 562 are communicated with each other throughthe communication holes 573, so that a (second) pressure chamber 523 isformed radially inwardly of the edge bag 504.

A fluid passage 34 comprising tubes and connectors communicates with thespace 560 in the torque transmitting member 507. The space 560 isconnected to the compressed air source 120 via a regulator R4 connectedto the fluid passages 34. A fluid passage 35 comprising tubes andconnectors communicates with the space 561 between the edge bag 504 andthe torque transmitting member 507. The space 561 is connected to thecompressed air source 120 via a regulator R5 connected to the fluidpassages 35. A fluid passage 36 comprising tubes and connectorscommunicates with the space 562 disposed radially inwardly of the torquetransmitting member 507. The space 562 is connected to the compressedair source 120 via a regulator (not shown) connected to the fluidpassages 36. The pressure chambers 521 to 523 are connected to therespective regulators through a rotary joint (not shown) mounted on theupper end of the top ring shaft 110.

Since the space 561, the space 560, and the space 562 are communicatedwith each other, as described above, one fluid passage can supply apressurized fluid so as to uniformly control the pressure of thepressure chamber 523 without a plurality of fluid passages. However, inorder to obtain good responsiveness when the pressure of the pressurechamber 523 is varied, it is desirable to provide a plurality of fluidpassages 34, 35, 36 as described in the third embodiment. It is notnecessary to provide regulators for the respective fluid passages 34,35, 36, and the fluid passages 34, 35, 36 maybe connected to oneregulator to control the pressure.

When the semiconductor wafer is polished, pressurized fluids aresupplied to the pressure chamber 522 and the pressure chamber 523,respectively. The flange 541 is provided at the lower end surface of theedge bag 504. The flange 541 is brought into close contact with thesemiconductor wafer W by the pressurized fluid supplied to the pressurechamber 523. Accordingly, the pressurized fluid in the pressure chamber523 is prevented from flowing into the lower portion of the edge bag504. Therefore, the flange 541 can realize a stable control when thepressures of the pressure chamber 522 and the pressure chamber 523 arevaried. Here, the radial width d of the elastic membrane defining thepressure chamber 522 in the edge bag 504 should preferably be in a rangeof from about 1 mm to about 10 mm in view of controlling a polishingrate at a peripheral portion of the semiconductor wafer W, and is set tobe 5 mm in the present embodiment.

The pressure chamber 521 above the chucking plate 506 and the pressurechambers 522, 523 are supplied with pressurized fluids such aspressurized air or atmospheric air or evacuated, via the fluid passages31, 33, 34 to 36 connected to the respective pressure chambers.Specifically, the regulators connected to the fluid passages 31, 33, 34to 36 of the pressure chambers 521 to 523 can respectively regulate thepressures of the pressurized fluids supplied to the respective pressurechambers. Thus, it is possible to independently control the pressures inthe pressure chambers 521 to 523 or independently introduce atmosphericair or vacuum into the pressure chambers 521 to 523. With thisarrangement, the pressures of the pressure chambers 523 can press theentire surface of the semiconductor wafer W except the peripheralportion thereof at a uniform force, and the pressure of the pressurechamber 522 can be controlled independently of the pressure of thepressure chamber 523. Therefore, it is possible to control a polishingrate at the peripheral portion of the semiconductor wafer W, i.e., apolishing profile of the peripheral portion of the semiconductor waferW. Additionally, when the pressing force of the retainer ring 3 iscontrolled, more detailed control can be achieved.

In this case, the pressurized fluid or the atmospheric air supplied tothe pressure chambers 522, 523 may independently be controlled intemperature. With this configuration, it is possible to directly controlthe temperature of a workpiece such as a semiconductor wafer from thebackside of the surface to be polished. Particularly, when each of thepressure chambers is independently controlled in temperature, the rateof chemical reaction can be controlled in the chemical polishing processof CMP.

The chucking plate 506 has suction portions 540 extended downwardlytherefrom between the edge bag 504 and the torque transmitting member507. In the present embodiment, four suction portions 540 are provided.The suction portions 540 have communication holes 540 a communicatingwith a fluid passage 37 comprising tubes and connectors. The suctionportions 540 are connected to the compressed air source 120 via aregulator (not shown) connected to the fluid passage 37. The compressedair source 120 can develop a negative pressure at the lower opening endsof the communication holes 540 a of the suction portion 540 to attract asemiconductor wafer W to the lower ends of the suction portions 540. Thesuction portions 540 have elastic sheets 540 b, such as thin rubbersheets, attached to their lower ends, for thereby elastically contactingand holding the semiconductor wafer W on the lower surfaces thereof.

Next, operation of the top ring 1 thus constructed will be described indetail below.

In the polishing apparatus constructed above, when a semiconductor waferW is to be delivered to the polishing apparatus, the top ring 1 as awhole is moved to a position to which the semiconductor wafer W istransferred, and the communication holes 540 a of the suction portions540 are connected via the fluid passage 37 to the compressed air source120. The semiconductor wafer W is attracted under vacuum to the lowerends of the suction portions 540 by suction effect of the communicationholes 540 a. With the semiconductor wafer W attracted to the top ring 1,the top ring 1 as a whole is moved to a position above the polishingtable 100 having the polishing surface (polishing pad 101) thereon. Theouter circumferential edge of the semiconductor wafer W is held by theretainer ring 3 so that the semiconductor wafer W is not removed fromthe top ring 1.

For polishing the semiconductor wafer W, the attraction of semiconductorwafer W by the suction portions 540 is released, and the semiconductorwafer W is held on the lower surface of the top ring 1. Simultaneously,the top ring air cylinder 111 connected to the top ring drive shaft 11is actuated to press the retainer ring 3 fixed to the lower end of thetop ring 1 against the polishing surface on the polishing table 100under a predetermined pressure. In such a state, pressurized fluids arerespectively supplied to the pressure chamber 522 and the pressurechamber 523 under respective pressures, thereby pressing thesemiconductor wafer W against the polishing surface on the polishingtable 100. The polishing liquid supply nozzle 102 supplies a polishingliquid Q onto the polishing pad 101 in advance, so that the polishingliquid Q is held on the polishing pad 101. Thus, the semiconductor waferW is polished by the polishing pad 101 with the polishing liquid Q beingpresent between the (lower) surface, to be polished, of thesemiconductor wafer W and the polishing pad 101.

The local areas of the semiconductor wafer W that are positioned beneaththe pressure chamber 522 and the pressure chamber 523 are pressedagainst the polishing surface under the pressures of the pressurizedfluids supplied to the pressure chamber 522 and the pressure chamber523. Therefore, by controlling the pressurized fluids supplied to thepressure chamber 522 and the pressure chamber 523, the polishingpressure applied to the semiconductor wafer W is adjusted so as to pressthe entire surface of the semiconductor wafer W except the peripheralportion thereof against the polishing surface at a uniform force.Simultaneously, a polishing rate at the peripheral portion of thesemiconductor wafer W can be controlled to control a polishing profileof the peripheral portion of the semiconductor wafer W. Similarly, theregulator R2 regulates the pressure of the pressurized fluid supplied tothe pressure chamber 521 to change the pressing force to press theretainer ring 3 against the polishing pad 101. In this manner, duringpolishing, the pressing force to press the retainer ring 3 against thepolishing pad 101 and the pressing force to press the semiconductorwafer W against the polishing pad 101 are properly adjusted to controlthe polishing profile of the peripheral portion of the semiconductorwafer W in great detail. The semiconductor wafer W located below thepressure chamber 523 has an area to which a pressing force is appliedvia the abutment portion 571 b of the torque transmitting member 507 bya fluid, and an area to which a pressure of the pressurized fluid isdirectly applied. The pressing forces applied to these areas have thesame pressure.

As described above, the pressing force applied by the top ring aircylinder 111 to press the retainer ring 3 against the polishing pad 101and the pressing forces applied by the pressurized fluids supplied tothe pressure chamber 522 and the pressure chamber 523 to press thesemiconductor wafer W against the polishing pad 101 are appropriatelyadjusted to polish the semiconductor wafer W. When the polishing of thesemiconductor wafer W is finished, the semiconductor wafer W isattracted to the lower ends of the suction portions 540 under vacuum. Atthis time, the supply of the pressurized fluids into the pressurechamber 522 and the pressure chamber 523 is stopped, and the pressurechamber 522 and the pressure chamber 523 are vented to the atmosphere.Accordingly, the lower ends of the suction portions 540 are brought intocontact with the semiconductor wafer W. The pressure chamber 521 isvented to the atmosphere or evacuated to develop a negative pressuretherein. This is because if the pressure chamber 521 is maintained at ahigh pressure, then the semiconductor wafer W is strongly pressedagainst the polishing surface only in areas brought into contact withthe suction portions 540.

After attraction of the semiconductor wafer W, the top ring 1 as a wholeis moved to a position to which the semiconductor wafer W is to betransferred, and then a fluid (e.g., compressed air or a mixture ofnitrogen and pure water) is ejected to the semiconductor wafer W via thecommunication holes 540 a of the suction portions 540 to release thesemiconductor wafer W from the top ring 1.

The polishing liquid Q used to polish the semiconductor wafer W tends toflow through the small gap G between the outer circumferential surfaceof the edge bag 504 and the retainer ring 3. If the polishing liquid Qis firmly deposited in the gap G, then the holder ring 505, the chuckingplate 506, and the edge bag 504 are prevented from smoothly movingvertically with respect to the top ring body 2 and the retainer ring 3.To avoid such a drawback, a cleaning liquid (pure water) is suppliedthrough the fluid passage 32 to the cleaning liquid passage 551.Accordingly, the pure water is supplied via a plurality of communicationholes 553 to a region above the gap G, thus cleaning the gap G toprevent the polishing liquid Q from being firmly deposited in the gap G.The pure water should preferably be supplied after the polishedsemiconductor wafer W is released and until a next semiconductor waferto be polished is attracted to the top ring 1.

In the third embodiment described above, the fluid passages 31, 33 to 37are provided as separate passages. However, these fluid passages may becombined with each other, or the pressure chambers may be communicatedwith each other in accordance with the magnitude of the pressing forceto be applied to the semiconductor wafer W and the position to which thepressing force is applied.

In the third embodiment shown in FIGS. 20 through 22, the polishingsurface is constituted by the polishing pad. However, the polishingsurface is not limited to this. The polishing surface may be constitutedby a fixed abrasive, as described in the first embodiment.

As described above, according to the third embodiment of the presentinvention, sufficient torque can be transmitted to the substrate by thetorque transmitting member. Further, the entire surface of the substrateexcept the peripheral portion thereof can be pressed against thepolishing surface at a uniform force by the pressure of the secondpressure chamber, and the pressure of the first pressure chamber can becontrolled independently of the pressure of the second pressure chamber.Therefore, it is possible to control a polishing rate at the peripheralportion of the semiconductor wafer W, i.e., a polishing profile of theperipheral portion of the semiconductor wafer W.

INDUSTRIAL APPLICABILITY

The present invention is suitable for use in a substrate holdingapparatus for holding a substrate such as a semiconductor wafer in apolishing apparatus for polishing the substrate to a flat finish, and apolishing apparatus having such a substrate holding apparatus.

1. A substrate holding apparatus for holding and pressing a substrate tobe polished against a polishing surface, characterized in that: saidsubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within said receiving space in said top ring body; an abutmentmember having an elastic membrane is attached to a lower surface of saidvertically movable member; said elastic membrane of said abutment membercomprises an abutment portion, having a flange projecting outwardly,brought into direct or indirect contact with the substrate, and aconnecting portion extending upwardly from a base portion of said flangeof said abutment portion and being connected to said vertically movablemember; and said connecting portion is made of a material having aflexibility higher than said abutment portion.
 2. A substrate holdingapparatus for holding and pressing a substrate to be polished against apolishing surface, characterized in that: said substrate holdingapparatus comprises a top ring body having a receiving space therein,and a vertically movable member which is vertically movable within saidreceiving space in said top ring body; an abutment member having anelastic membrane is attached to a lower surface of said verticallymovable member; said elastic membrane of said abutment member comprisesan abutment portion, having a flange projecting outwardly, brought intodirect or indirect contact with the substrate, and a connecting portionextending upwardly from a base portion of said flange of said abutmentportion and being connected to said vertically movable member; and saidconnecting portion comprises a thin portion having a thickness smallerthan said abutment portion.
 3. A substrate holding apparatus accordingto claim 2, characterized in that said thin portion is formed so as tobe constricted inwardly in a cross-section.
 4. A substrate holdingapparatus for holding and pressing a substrate to be polished against apolishing surface, characterized in that: said substrate holdingapparatus comprises a top ring body having a receiving space therein,and a vertically movable member which is vertically movable within saidreceiving space in said top ring body; an abutment member having anelastic membrane is attached to a lower surface of said verticallymovable member; said elastic membrane of said abutment member comprisesan abutment portion, having a flange projecting outwardly, brought intodirect or indirect contact with the substrate, and a connecting portionextending upwardly from a base portion of said flange of said abutmentportion and being connected to said vertically movable member; andadhesiveness of a lower surface of said base portion of said flange ofsaid abutment portion is weakened.
 5. A substrate holding apparatusaccording to claim 4, characterized in that an intermediate memberhaving a low adhesiveness to the substrate is disposed on said lowersurface of said base portion of said flange of said abutment portion toweaken adhesiveness of said lower surface of said base portion of saidflange.
 6. A substrate holding apparatus for holding and pressing asubstrate to be polished against a polishing surface, characterized inthat: said substrate holding apparatus comprises a top ring body havinga receiving space therein, and a vertically movable member which isvertically movable within said receiving space in said top ring body; anabutment member having an elastic membrane is attached to a lowersurface of said vertically movable member; said elastic membrane of saidabutment member comprises an abutment portion, having a flangeprojecting outwardly, brought into direct or indirect contact with thesubstrate, and a connecting portion extending upwardly from a baseportion of said flange of said abutment portion and being connected tosaid vertically movable member; and a hard member made of a materialharder than said elastic membrane is embedded in said base portions ofsaid flange of said abutment portion.
 7. A substrate holding apparatusaccording to claim 6, characterized in that said hard member has anannular shape.
 8. A substrate holding apparatus for holding and pressinga substrate to be polished against a polishing surface, characterized inthat: said substrate holding apparatus comprises a top ring body havinga receiving space therein, and a vertically movable member which isvertically movable within said receiving space in said top ring body; anabutment member having an elastic membrane is attached to a lowersurface of said vertically movable member; and said elastic membrane ofsaid abutment member comprises an abutment portion, having a flangeprojecting outwardly, brought into direct or indirect contact with thesubstrate, an extending portion extending outwardly from a base portionof said flange to a position inward of a tip of said flange to form agroove between said extending portion and said flange of said abutmentportion, and a connecting portion extending upwardly from an outward endof said extending portion and being connected to said vertically movablemember.
 9. A substrate holding apparatus according to claim 1,characterized in that said connecting portion positioned radiallyinwardly and said connecting portion positioned radially outwardly havedifferent thicknesses.
 10. A substrate holding apparatus according toclaim 9, characterized in that said connecting portion positionedradially inwardly has a thickness smaller than said connecting portionpositioned radially outwardly.
 11. A substrate holding apparatusaccording to claim 1, characterized in that said flange projectingradially outwardly and said flange projecting radially inwardly havedifferent lengths.
 12. A substrate holding apparatus according to claim11, characterized in that said flange projecting radially outwardly hasa length larger than said flange projecting radially inwardly.
 13. Asubstrate holding apparatus for holding and pressing a substrate to bepolished against a polishing surface, characterized in that: saidsubstrate holding apparatus comprises a top ring body having a receivingspace therein, and a vertically movable member which is verticallymovable within said receiving space in said top ring body; an abutmentmember having an elastic membrane which is brought into direct orindirect contact with the substrate is attached to a lower surface ofsaid vertically movable member; and said vertically movable member ismade of a material having a large stiffness.
 14. A substrate holdingapparatus for holding and pressing a substrate to be polished against apolishing surface, characterized in that: an abutment member having anelastic membrane is attached to a lower surface of a top ring; saidelastic membrane of said abutment member comprises an abutment portion,having a flange projecting outwardly, brought into direct or indirectcontact with the substrate, and a connecting portion extending upwardlyfrom a base portion of said flange of said abutment portion and beingconnected to said top ring; and said top ring has a support portion forsupporting said flange of said abutment member.
 15. A substrate holdingapparatus according to claim 14, characterized in that said supportportion has a radial length larger than a radial length of said flangeof said abutment member.
 16. A substrate holding apparatus according toclaim 14, characterized in that a fluid introduction groove forintroducing a fluid into an upper surface of said flange of saidabutment member is formed in said support portion.
 17. A substrateholding apparatus for holding and pressing a substrate to be polishedagainst a polishing surface, characterized in that: said substrateholding apparatus comprises a top ring body having a receiving spacetherein, a vertically movable member which is vertically movable withinsaid receiving space in said top ring body, and a seal ring beingbrought into contact with an upper surface of a peripheral portion ofthe substrate; and said vertically movable member has a support portionfor supporting said seal ring, said support portion having a radiallength in a range of from 1 mm to 7 mm.
 18. A substrate holdingapparatus according to claim 17, characterized in that a fluidintroduction groove for introducing a fluid into an upper surface ofsaid seal ring is formed in said support portion of said verticallymovable member.
 19. A substrate holding apparatus for holding andpressing a substrate to be polished against a polishing surface,characterized in that: said substrate holding apparatus comprises a topring body for holding the substrate, an edge bag being brought intocontact with a peripheral portion of the substrate, a torquetransmitting member being brought into contact with the substrateradially inwardly of said edge bag; and a pressure of a first pressurechamber defined in said edge bag and a pressure of a second pressurechamber defined radially inwardly of said edge bag are independentlycontrolled.
 20. A substrate holding apparatus according to claim 19,characterized in that said torque transmitting member has acommunication hole communicating a space inside of said torquetransmitting member and a space outside of said torque transmittingmember with each other.
 21. A substrate holding apparatus according toclaim 19, characterized in that said edge bag defining said firstpressure chamber comprises a member having a radial width in a range offrom 1 mm to 10 mm.
 22. A substrate holding apparatus according to claim19, characterized in that: said substrate holding apparatus comprises aretainer ring secured to or formed integrally with said top ring bodyfor holding a side edge portion of the substrate; and a pressing forceto press said retainer ring against the polishing surface is controlledindependently of a pressure of said pressure chamber.
 23. A polishingapparatus characterized by comprising a substrate holding apparatusaccording to claim 1, and a polishing table having a polishing surface.24. A substrate holding apparatus according to claim 2, characterized inthat said connecting portion positioned radially inwardly and saidconnecting portion positioned radially outwardly have differentthicknesses.
 25. A substrate holding apparatus according to claim 4,characterized in that said connecting portion positioned radiallyinwardly and said connecting portion positioned radially outwardly havedifferent thicknesses.
 26. A substrate holding apparatus according toclaim 6, characterized in that said connecting portion positionedradially inwardly and said connecting portion positioned radiallyoutwardly have different thicknesses.
 27. A substrate holding apparatusaccording to claim 8, characterized in that said connecting portionpositioned radially inwardly and said connecting portion positionedradially outwardly have different thicknesses.
 28. A substrate holdingapparatus according to claim 24, characterized in that said connectingportion positioned radially inwardly has a thickness smaller than saidconnecting portion positioned radially outwardly.
 29. A substrateholding apparatus according to claim 25, characterized in that saidconnecting portion positioned radially inwardly has a thickness smallerthan said connecting portion positioned radially outwardly.
 30. Asubstrate holding apparatus according to claim 26, characterized in thatsaid connecting portion positioned radially inwardly has a thicknesssmaller than said connecting portion positioned radially outwardly. 31.A substrate holding apparatus according to claim 27, characterized inthat said connecting portion positioned radially inwardly has athickness smaller than said connecting portion positioned radiallyoutwardly.
 32. A substrate holding apparatus according to claim 2,characterized in that said flange projecting radially outwardly and saidflange projecting radially inwardly have different lengths.
 33. Asubstrate holding apparatus according to claim 4, characterized in thatsaid flange projecting radially outwardly and said flange projectingradially inwardly have different lengths.
 34. A substrate holdingapparatus according to claim 6, characterized in that said flangeprojecting radially outwardly and said flange projecting radiallyinwardly have different lengths.
 35. A substrate holding apparatusaccording to claim 8, characterized in that said flange projectingradially outwardly and said flange projecting radially inwardly havedifferent lengths.
 36. A substrate holding apparatus according to claim32, characterized in that said flange projecting radially outwardly hasa length larger than said flange projecting radially inwardly.
 37. Asubstrate holding apparatus according to claim 33, characterized in thatsaid flange projecting radially outwardly has a length larger than saidflange projecting radially inwardly.
 38. A substrate holding apparatusaccording to claim 34, characterized in that said flange projectingradially outwardly has a length larger than said flange projectingradially inwardly.
 39. A substrate holding apparatus according to claim35, characterized in that said flange projecting radially outwardly hasa length larger than said flange projecting radially inwardly.
 40. Apolishing apparatus characterized by comprising a substrate holdingapparatus according to claim 2, and a polishing table having a polishingsurface.
 41. A polishing apparatus characterized by comprising asubstrate holding apparatus according to claim 4, and a polishing tablehaving a polishing surface.
 42. A polishing apparatus characterized bycomprising a substrate holding apparatus according to claim 6, and apolishing table having a polishing surface.
 43. A polishing apparatuscharacterized by comprising a substrate holding apparatus according toclaim 8, and a polishing table having a polishing surface.
 44. Apolishing apparatus characterized by comprising a substrate holdingapparatus according to claim 13, and a polishing table having apolishing surface.
 45. A polishing apparatus characterized by comprisinga substrate holding apparatus according to claim 14, and a polishingtable having a polishing surface.
 46. A polishing apparatuscharacterized by comprising a substrate holding apparatus according toclaim 17, and a polishing table having a polishing surface.
 47. Apolishing apparatus characterized by comprising a substrate holdingapparatus according to claim 19, and a polishing table having apolishing surface.